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Efflux Of Osmolyte Amino Acids During Isovolumic Regulation In Hippocampal Slices, Rodrigo Franco, Octavio Quesada, Herminia Pasantes-Morales

School of Veterinary and Biomedical Sciences: Faculty Publications

The efflux of potassium (K⁺) and amino acids from hippocampal slices was measured after sudden exposure to 10% (270 mOsm), 25% (225 mOsm) or 50% (150 mOsm) hyposmotic solutions or after gradual decrease (22.5 mOsm/min) in external osmolarity. In slices suddenly exposed to 50% hyposmotic solutions, swelling was followed by partial (74%) cell volume recovery, suggesting regulatory volume decrease (RVD). With gradual hyposmotic changes, no increase in cell water content was observed even when the solution at the end of the experiment was 50% hyposmotic, showing the occurrence of isovolumic regulation (IVR). The gradual decrease in osmolarity elicited …

Effect Of Chlamydia Trachomatis Infection And Subsequent Tnfa Secretion On Apoptosis In The Murine Genital Tract, Jean-Luc Perfettini, Toni Darville, Gabriel Gachelin, Philippe Souque, Michel Huerre, Alice Dautry-Varsat, David M. Ojcius

All Dugoni School of Dentistry Faculty Articles

The pathology observed during Chlamydia infection is due initially to localized tissue damage caused by the infection itself, followed by deleterious host inflammatory responses that lead to permanent scarring. We have recently reported that the infection byChlamydia in vitro results in apoptosis of epithelial cells and macrophages and that infected monocytes secrete the proinflammatory cytokine interleukin-1β. At the same time, proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α) can also trigger apoptosis of susceptible cells. To study the possible relationship between Chlamydia trachomatis infection and apoptosis in vivo, we used the terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling technique to …

Absence Of Insect Juvenile Hormones In The American Dog Tick, Dermacentor Veriabilis (Say) (Acari: Ixodidae), And In Ornithodoros Parkeri Cooley (Acari: Argasidae), P. A. Neese, Daniel E. Sonenshine, V. L. Kallapur, C. S. Apperson, R. M. Roe

Biological Sciences Faculty Publications

Synganglia, salivary gland, midgut, ovary, fat body and muscle alone and in combination from the ixodid tick, Dermacentor variabilis (Say), or the argasid tick, Ornithodoros parkeri Cooley, were incubated in vitro in separate experiments with _L-[methyl-³H]methionine and farnesoic acid or with [1-¹⁴C]acetate. Life stages examined in D. variabilis were 3 and 72 h old (after ecdysis) unfed nymphs, partially fed nymphs (18 and 72 h after attachment to the host), fully engorged nymphs (2 d after detachment from host), 3 and 72 h old (after eclosion) unfed females, partially fed unmated females (12–168 …

Isovolumic Regulation In Nervous Tissue: A Novel Mechanism Of Cell Volume Regulation, O. Quesada, R. Franco, K. Hernandez-Fonseca, K. Tuz

School of Veterinary and Biomedical Sciences: Faculty Publications

Cell volume regulation is a property present in most animal cell lineages that allows them to recover their original volume after events of swelling or shrinkage. Such events can be caused by changes in external osmolarity or to osmotic gradients generated during normal cell functioning.4,6 The mechanism of cell volume regulation involves transmembrane fluxes of osmotically active solutes in the necessary direction to counteract the net gain or loss of intracellular water.9 The process through which cells recover their normal volume after swelling is named Regulatory Volume Decrease (RVD). This consists of the efflux of inorganic osmolytes, such as K …

Cytotoxic T Cell Response To Influenza Vaccination In Older Adults, Caroline R. Letter

Chemistry & Biochemistry Theses & Dissertations

Influenza infections result in activation of cellular and humoral immune responses, leading to stimulation of cytotoxic T cells (CTL) and helper T cells with subsequent viral clearance.

By using an assay of granzyme B activity, the in vivo cellular-mediated immune response of old adults was found to be significantly decreased in comparison to young adults. The effect of aging on the CTL response was further investigated via enzyme-linked immunospot technique. A significant increase in number of virus-specific T cells occurred in older adults after vaccination, although the magnitude of the CTL response decreased in comparison to young adults. These data …

Optimal Replication Activity Of Vesicular Stomatitis Virus Rna Polymerase Requires Phosphorylation Of A Residue(S) At Carboxy-Terminal Domain Ii Of Its Accessory Subunit, Phosphoprotein P, Leroy N. Hwang, Nathan Englund, Tapas Das, Amiya K. Florida, Asit K. Pattnaik

School of Veterinary and Biomedical Sciences: Faculty Publications

The phosphoprotein, P, of vesicular stomatitis virus (VSV) is a key subunit of the viral RNA-dependent RNA polymerase complex. The protein is phosphorylated at multiple sites in two different domains. We recently showed that specific serine and threonine residues within the amino-terminal acidic domain I of P protein must be phosphorylated for in vivo transcription activity, but not for replication activity, of the polymerase complex. To examine the role of phosphorylation of the carboxy-terminal domain II residues of the P protein in transcription and replication, we have used a panel of mutant P proteins in which the phosphate acceptor sites …

Nucleotide Sequences For Detection Of Serpulina Hyodysenteriae, Gerald E. Duhamel, Robert Elder

School of Veterinary and Biomedical Sciences: Faculty Publications

The invention provides a method for detecting the presence of Serpulina hyodysenteriae in a biological Sample, an oligonucleotide primer and an S. hyodysenteriae-specific oligonucleotide probe useful in that method, and an article of manufacture that contains the primers and/or probe. Also provided are an about 2.3-kb DNA fragment derived from genomic DNA of S. hyodysenteriae and encoding for an about 56 kDa polypeptide, a recombinant expression vector containing the DNA fragment, the 56 kDa polypeptide and a monoclonal antibody reactive with the peptide, and a method of assaying for antibodies reactive with the 56 kDa peptide.

Levels Of Major Selenoproteins In T Cells Decrease During Hiv Infection And Low Molecular Mass Selenium Compounds Increase, Vadim Gladyshev, Thressa C. Stadtman, Dolph L. Hatfield, Kuan-Teh Jeang

Vadim Gladyshev Publications

It has been observed previously that plasma selenium and glutathione levels are subnormal in HIV-infected individuals, and plasma glutathione peroxidase activity is decreased. Under these conditions the survival rate of AIDS patients is reduced significantly. In the present study, using ⁷⁵Se-labeled human Jurkat T cells, we show that the levels of four ⁷⁵Se-containing proteins are lower in HIV-infected cell populations than in uninfected cells. These major selenoproteins migrated as 57-, 26-, 21-, and 15-kDa species on SDS/PAGE gels. In our earlier studies, the 57-kDa protein was purified from T cells and identified as a subunit of thioredoxin reductase. …

The Atomic Force Microscope In The Elucidation Of Leukocyte Abnormality, Derbrenn O'Connor

Theses

The aim of this project was to investigate the novel use of the atomic force microscope (AFM) as a technique in the elucidation of leukocyte abnormality. To this end, comparative AFM imaging and elasticity studies were performed on normal and myeloid leukaemic leukocytes.

Initially, an evaluation of techniques for the isolation of specific leukocyte (e.g. lymphocytes, granulocytes, etc.) populations from whole blood or leukocyte concentrates, was carried out. It was found that a silanised glass surface failed to select and immobilise a leukocyte population. However, centrifugation of whole blood in an Isopaque-ficoll gradient solution yielded a viable mixed leukocyte population …

Plasmd Bearing A Cdna Copy Of The Genome Of Bovine Viral Diarrhea Virus, Chimeric Derivatives Thereof, And Method Of Producing An Infectious Bovine Wral Darrheavirus Using Sad Plasmid, Ruben O. Donis, Ventzislav B. Vassilev

School of Veterinary and Biomedical Sciences: Faculty Publications

A plasmid bearing a cDNA copy of the genome of bovine viral diarrhea virus (BVDV), chimeric derivatives of the plasmid and a method of producing an infectious bovine viral diarrhea virus using the plasmid are disclosed. The invention relates to a plasmid DNA molecule that replicates easily in E. coli and contains a sufficient portion of the genome of BVDV, cloned as cDNA, to be a suitable template to produce RNA in vitro which, upon transfection into bovine cells, gives rise to infectious BVDV. The BVDV created by the process of the invention can be engineered for use as a …

In Situ Hybridization For The Detection And Localization Of Swine Chlamydia Trachomatis, C. Chae, D.-S. Cheon, D. Kwon, O. Kim, B. Kim, J. Suh, D. G. Rogers, K. D. E. Everett, A. A. Anderson

School of Veterinary and Biomedical Sciences: Faculty Publications

Gnotobiotic piglets were inoculated intralaryngeally with swine Chlamydia trachomatis strain R33 or orally with swine C. trachmatis strain R27. Archived formalin-fixed, paraffin-embedded tissues from piglets euthanatized 4–7 days postinoculation were examined by in situ hybridization for C. trachomatis nucleic acid using a nonradioactive digoxigenin-labeled DNA probes that targeted specific ribosomal RNA or omp1 mRNA molecules of the swine C. trachomatis strains. Positive hybridization signals were detected in bronchial epithelial cells, bronchiolar epithelial cells, pneumocytes, alveolar and interstitial macrophages, and jejunal and ileal enterocytes. Chlamydia-infected cells had a strong signal that was confined to the intracytoplasmic inclusions. Positive hybridization signals were …

Carmoviruses (Tombusviridae), Feng Qu, Thomas Jack Morris

School of Biological Sciences: Faculty Publications

Carmovirus is one of two officially recognized genera of Tombusviridae. Members of Tombusviridae all have icosahedral virions of about 30 nm in diameter with T = 3 symmetry that consists of 180 coat protein (CP) subunits of about 38- 43 kDa and a single-stranded (ss) RNA genome ranging in size from 4.0 to 4.7 kb. Carmoviruses share recognizable sequence similarity in both the polymerase and structural genes with members of the other genus, Tombusvirus. Sequence comparisons and phylogenetic analysis of these genes support the view that the genera are distinct but closely related. In addition, the genome organization of the …

Detection Of Ehrlichia Chaffeensis In Ticks Of The Georgia Coast And Barrier Islands Using Polymerase Chain Reaction, John Edward Whitlock

College of Graduate Studies: Theses & Dissertations (1964–2006)

Human monocytic ehrlichiosis (HME) is an emerging, zoonosis transmitted to mammals by ixodid ticks. Prevalence of infected ticks and distribution of infection foci indicate relative risk of human exposure to ehrlichiosis and may be influenced by factors such as geographic isolation and human disturbance. To test this, individual and pooled lone star ticks, Amblyomma americanum (L.), collected from 3 populations from the coast and barrier islands of Georgia were screened for Ehrlichia chaffeensis Anderson, Dawson, Jone, and Wilson, the agent of HME. A species-specific, nested polymerase chain reaction (PGR) assay was used to amplify a 572 base pair fragment of …

Enhancement Of Atp Levels And Glucose Metabolism During An Infection By Chlamydia: Nmr Studies Of Living Cells, David M. Ojcius, H. Degani, Joel Mispelter, Alice Dautry-Varsat

All Dugoni School of Dentistry Faculty Articles

The Chlamydia species are obligate intracellular bacteria that proliferate only within the infected cell. Since the extracellular bacteria are metabolically inert and there are no cell-free systems for characterizingChlamydia metabolism, we studied metabolic changes related to ATP synthesis and glycolysis in HeLa cells infected withChlamydia psittaci during the course of the 2-day infection cycle using noninvasive 31P and 13C NMR methods. We find that the infection stimulates ATP synthesis in the infected cell, with a peak of ATP levels occurring midway through the infection cycle, when most of the metabolically active bacteria are proliferating. The infection also stimulates synthesis of …

Polyadenylation Of Vesicular Stomatitis Virus Mrna Dictates Efficient Transcription Termination At The Intercistronic Gene Junctions, Leroy N. Hwang, Nathan Englund, Asit K. Pattnaik

School of Veterinary and Biomedical Sciences: Faculty Publications

The intercistronic gene junctions of vesicular stomatitis virus (VSV) contain conserved sequence elements that are important for polyadenylation and transcription termination of upstream transcript as well as reinitiation of transcription of downstream transcript. To examine the role of the putative polyadenylation signal 3' AUACU₇5' at the gene junctions in polyadenylation and transcription termination, we constructed plasmids encoding antigenomic minireplicons containing one or two transcription units. In plasmid-transfected cells, analyses of the bicistronic minireplicon containing the wild-type or mutant intercistronic gene junctions for the ability to direct synthesis of polyadenylated upstream, downstream, and readthrough mRNAs showed that the AUACU …

Diphtheria Toxin Fusion Proteins, Frank Foss, Mansoor Saleh, James Krueger, John Nichols, John Murphy

Haematology and Oncology, East Africa

Two different approaches have been undertaken to develop targeted biomolecules for therapeutics. The first was the construction of immunotoxins consisting of monoclonal antibodies chemically linked through a disulfide bond to a plant or bacterial toxin or radionuclide. Instability of the chemical conjugation of some of the earlier immunotoxins led to the concept of using protein engineering and recombinant DNA to assemble fusion genes combining the sequences for the enzymatically active and translocation domains of a toxin with those of a specific targeting ligand. From the outset, the prospect of using recombinant DNA methods to assemble the structural genes encoding bacterial …

Distribution Of Endosomal, Lysosomal And Mhc Markers In A Monocytic Cell Line Infected With Chlamydia Psittaci, David M. Ojcius, Raymond Hellio, Alice Dautry-Varsat

All Dugoni School of Dentistry Faculty Articles

The intracellular fate of Chlamydia psittaci during infection of a monocytic cell line, THP1, was characterized. Cytochalasin D inhibited phagocytosis of latex beads but had no effect on infection by C. psittaci, and vacuoles expressed the transferrin receptor, suggesting accessibility to the endocytic pathway. Early Chlamydia-containing vacuoles expressed major histocompatibility complex (MHC) class I molecules, and most vacuoles fused with host cell lysosomes, since they expressed LAMP-1 and had acidic pHs. In cells prestimulated with gamma interferon, vacuoles also expressed MHC class II molecules, suggesting that the monocytes might effectively process Chlamydia-derived antigens for presentation by MHC class I and …

An Immunomodulating Mycotoxin Interferes With The Development Of Autoimmune Diabetes In Diabetes-Prone Bb/Wor Rats, Honggang Liu

Theses, Dissertations and Capstones

Various fungal products have immunomodulating activity and some have been studied regarding prevention of transplantation rejection. Prior to this investigation, the mycotoxin, gliotoxin (GT), has never been investigated as an immunotherapeutic drug for autoimmune disease. GT is a fungal secondary metabolite and a member of the epipolythiodioxopiperazine (ETP) family which has been shown to inhibit phagocytosis, induction of cytolytic T cells and the proliferation of T cells following mitogen stimulation. GT also induces in vitro apoptosis in certain immune cell types. More importantly, GT exhibits selective activity towards cells of hemopoietic origin.

Autoimmune diseases are disorders caused by immune responses …

Phosphorylation Within The Amino-Terminal Acidic Domain I Of The Phosphoprotein Of Vesicular Stomatitis Virus Is Required For Transcription But Not For Replication, Asit K. Pattnaik, Leroy Hwang, Tong Le, Nathan Englund, Manjula Mathur, Tapas Das, Amiya Banerjee

School of Veterinary and Biomedical Sciences: Faculty Publications

Phosphorylation by casein kinase II at three specific residues (S-60, T-62, and S-64) within the acidic domain I of the P protein of Indiana serotype vesicular stomatitis virus has been shown to be critical for in vitro transcription activity of the viral RNA polymerase (P-L) complex. To examine the role of phosphorylation of P protein in transcription as well as replication in vivo, we used a panel of mutant P proteins in which the phosphate acceptor sites in domain I were substituted with alanines or other amino acids. Analyses of the alanine-substituted mutant P proteins for the ability to support …

Interleukin-10 Inhibits Tumor Metastasis Through An Nk-Cell Dependent Mechanism, Li-Mou Zheng, David M. Ojcius, F. Garaud, C. Roth, E. Maxwell, Z. Li, H. Rong, J. Chen, X. Y. Wang, J. J. Catino, I. King

All Dugoni School of Dentistry Faculty Articles

Interleukin-10 (IL-10) is a recently described pleiotropic cytokine secreted mainly by type 2 helper T cells. Previous studies have shown that IL-10 suppresses cytokine expression by natural killer (NK) and type 1 T cells, thus down-regulating cell-mediated immunity and stimulating humoral responses. We here report that injected IL-10 protein is an efficient inhibitor of tumor metastasis in experimental (B16-F10) and spontaneous (M27 and Lox human melanoma) metastasis models in vivo at doses that do not have toxic effects on normal or cancer cells. Histological characterization after IL-10 treatment confirmed the absence of CD8+ and CD4+ T cells and macrophages at …

Selenocysteine, Identified As The Penultimate C-Terminal Residue In Human T-Cell Thioredoxin Reductase, Corresponds To Tga In The Human Placental Gene, Vadim Gladyshev, Kuan-Teh Jeang, Thressa C. Stadtman

Vadim Gladyshev Publications

The possible relationship of selenium to immunological function which has been suggested for decades was investigated in studies on selenuim metabolism in human T cells. One of the major ⁷⁵Se-labeled selenoproteins detected was purified to homogeneity and shown to be a homodimer of 55-kDa subunits. Each subunit contained about 1 FAD and at least 0.74 Se. This protein proved to be thioredoxin reductase (TR) on the basis of its catalytic activities, cross-reactivity with anti-rat liver TR antibodies, and sequence identities of several tryptic peptides with the published deduced sequence of human placental TR. Physicochemical characteristics of T-cell TR were …

The Lipooligosaccharides Of Haemophilus Ducreyi Are Highly Sialylated, William Melaugh, A A. Campagnari, B W. Gibson

Chemistry Faculty Publications

The major lipooligosaccharides of the sexually transmitted pathogen Haemophilus ducreyi 35000 have been previously found to terminate in N-acetyllactosamine and sialyl-N-acetyllactosamine, Neu5Ac alpha 2-->3Gal beta 1-->4GlcNAc (W. Melaugh, N. J. Phillips, A. A. Campagnari, M. V. Tullius, and B. W. Gibson, Biochemistry 33: 13070-13078, 1994). In this study, mass spectrometry and composition analyses have shown that the lipooligosaccharides from three other H. ducreyi strains also contain N-acetyllactosamine and are highly sialylated (approximately 30 to 50%), although one African strain was found to contain neither of these structural features.

Role Of Immunodominant T Cell Responses To Minor Histocompatibility Antigens In A Mouse Model Of Graft-Versus-Host Disease, Marc Adam Berger, B.S. Thomas Jefferson University

Full-Text Theses & Dissertations

Graft-versus-host-disease (GVHD) is a major complication of major histocompatibility complex (MHC) matched bone marrow transplantation. GVHD is the result of an immune-mediated attack, by T lymphocytes derived from donor bone marrow, against recipient tissues expressing minor histocompatibility antigen (miHA) differences. There is a lack of knowledge concerning the nature of in vivo immune responses to miHA during GVHD. C57BL/6By (B6/By) and BALB.B mouse strains both express the H-2B MHC haplotype but differ at more than 40 miHA loci. Both the in vitro and in vivo T cell responses to miHA expressed by BALB.B and CXB recombinant inbred (RI) strains of …

Bovine Cell Line Resistant To In Vtro Infection By Bovine Viral Darrheavirus And All Other Known Pestiviruses, Ruben O. Donis, Eduardo F. Flores

School of Veterinary and Biomedical Sciences: Faculty Publications

Bovine cell line resistant to infection by the pestiviruses Bovine Viral Diarrhea Virus (BVDV), Hog Cholera Virus (HCV) and Border Disease Virus (BDV) and all progeny and mutants thereof. A bovine cell line (CRIB) that is resistant to infection by cytopathic and non-cytopathic BVDV and by other Pestiviruses due to a stable, recessive genetic defect which blocks infection at the level of viral entry.

Ph And Calcium Dependence Of Hemolysis Due To Rickettsia Prowazekii: Comparison With Phospholipase Activity, David M. Ojcius, M. Thibon, C. Mounier, Alice Dautry-Varsat

All Dugoni School of Dentistry Faculty Articles

Rickettsia prowazekii invades nucleated cells through phagocytosis and subsequently proliferates in the cytoplasm of the host cell. Hemolysis and a phospholipase A2 (PLA2) activity at neutral pHs have previously been reported; even though the phagosomal environment is most likely acidic. We here show that R. prowazekii and R. typhi also lyse erythrocytes at mildly acidic pHs, compatible with an early phagosomal compartment. For R. prowazekii, hemolysis at an acidic pH but not a neutral pH is enhanced by Ca2+, raising the possibility that more than one membranolytic factor may be produced by the rickettsiae. The rickettsiae alone display PLA2 activity, …

Heterozygosity Mapping Of Partially Congenic Lines: Mapping Of A Semidominant Neurological Mutation, Wheels ( Whl), On Mouse Chromosome 4, Patrick M. Nolan, Patricia J. Sollars, Barbara A. Bohne, Warren J. Ewens, Gary E. Pickard, Maja Bucan

School of Veterinary and Biomedical Sciences: Faculty Publications

We identified a semidominant, chemically induced, mouse use mutation with a complex array of abnormal behaviors including bidirectional circling and hyperactivity, abnormal circadian rhythmicity and abnormal responses to light. In this report, we genetically and phenotypically characterized the circling/ waltzing component of the abnormal behavior. We mapped the locus controlling this trait by heterozygosity mapping of partially congenic lines carrying the mutagenized chromosome outcrossed to different inbred strains for three generations. Analysis of 68 PCR-based markers in 13 affected individuals indicated that the mutant locus, named Wheels (Whl), resides in the subcentromeric portion of mouse chromosome 4. The …

Moraxella (Branhamella) Catarrhalis: A Molecular Epidemiology Study, Lyndell R. Gill

Electronic Theses and Dissertations

Moraxella (Branhamella) catarrhalis is the third-most-frequently isolated microorganism associated with acute exacerbations of chronic bronchitis in patients during their stay at the Mountain Home VA Medical Center (MHVAMC). In order to develop a practical, epidemiologically-meaningful typing method for M. (B.) catarrhalis, we tested two methods based on analysis of chromosomal DNA for typeability, reproducibility, and ability to differentiate between unrelated strains (discriminatory power, D). M. (B.) catarrhalis isolants from MHVAMC from 7/1/87-6/30/88 were grown overnight in broth and embedded in agarose. DNA was isolated by standard methods. The DNA was subjected to: (1) restriction endonuclease digestion (with either Bgl II …

Restoration Of Circadian Behavior By Anterior Hypothalamic Heterografts, Patricia J. Sollars, Daniel P. Kimble, Gary E. Pickard

School of Veterinary and Biomedical Sciences: Faculty Publications

The suprachiasmatic nucleus (SCN) of the anterior hypothalamus (AH) is a circadian oscillator and an important component of the mammalian circadian system. To determine whether the SCN is the dominant circadian pacemaker responsible for generating a species-typical characteristic of circadian rhythms [i.e., period length (T)], neural transplantation was conducted using fetal AH donors of different species and SCN-lesioned (SCNx) hosts. The circadian behavior of each of the three donor species is clearly distinguishable by its species-typical T. The extent of SCN pacemaker autonomy was assessed by noting whether the period of the restored circadian rhythm following heterograft transplantation was characteristic …

Certain Canine Weakly Β-Hemolytic Intestinal Spirochetes Are Phenotypically And Genotypically Related To Spirochetes Associated With Human And Porcine Intestinal Spirochetosis, Gerald E. Duhamel, Nagaraja Muniappa, Michelle R. Mathiesen, J. L. Johnson, J. Toth, R. O. Elder, A. R. Doster

School of Veterinary and Biomedical Sciences: Faculty Publications

Four canine weakly β-hemolytic intestinal spirochetes associated with intestinal spirochetosis (IS-associated WBHIS) were compared with IS-associated human and porcine WBHIS and the type species for Serpulina hyodysenteriae and S. innocens by using phenotypic and genotypic parameters. The IS-associated canine, human, and porcine WBHIS belonged to a phyletic group distinct from but related to previously described Serpulina type species.

Structure-Substrate Binding Relationships Of Hiv-1 Reverse Transcriptase, Steve Chien-Wen Huang

Theses and Dissertations in Biomedical Sciences

Human Immunodeficiency Virus, type 1 (HIV-1), is the causative agent of the Acquired Immunodeficiency Syndrome (AIDS). HIV-1 reverse transcriptase (RT), a heterodimer p66/p51, has been the major target for treatment of AIDS. The significance of the p51 subunit and the RNase H domain of p66 in terms of their influence on the RNA-dependent DNA synthesis was investigated. Clones of the wildtype HIV-1 RT subunits, p66 and p51, and a recombinant C-terminal deletion mutant, p64, [Barr, P. J. (1987) Bio/Technoloav 5, 486-489] were employed to study the structure-substrate binding relationships of HIV-1 RT. The activity assays of RNA-dependent DNA synthesis on …