Life Sciences Commons^™

Anaerobic Protoporphyrin Biosynthesis Does Not Require Incorporation Of Methyl Groups From Methionine, David Bollivar, Thomas Elliott, Samuel I. Beale

David Bollivar

It was recently reported (H. Akutsu, J.-S. Park, and S. Sano, J. Am. Chem. Soc. 115:12185–12186, 1993) that in the strict anaerobe methyl groups from exogenous L-methionine are incorporated specifically into the 1 and 3 positions (Fischer numbering system) on the heme groups of cytochrome c3. It was suggested that under anaerobic conditions, protoporphyrin IX biosynthesis proceeds via a novel pathway that does not involve coproporphyrinogen III as a precursor but instead may use precorrin-2 (1,3-dimethyluroporphyrinogen III), a siroheme and vitamin B12 precursor which is known to be derived from uroporphyrinogen III via methyl transfer from S-adenosyl-L-methionine. We have critically …

The Heterochronic Gene Lin-29 Encodes A Zinc Finger Protein That Controls A Terminal Differentiation Event In Caenorhabditis Elegans, Ann Rougvie, Victor Ambros

Victor R. Ambros

A hierarchy of heterochronic genes, lin-4, lin-14, lin-28 and lin-29, temporally restricts terminal differentiation of Caenorhabditis elegans hypodermal seam cells to the final molt. This terminal differentiation event involves cell cycle exit, cell fusion and the differential regulation of genes expressed in the larval versus adult hypodermis. lin-29 is the most downstream gene in the developmental timing pathway and thus it is the most direct known regulator of these diverse processes. We show that lin-29 encodes a protein with five zinc fingers of the (Cys)2-(His)2 class and thus likely controls these processes by regulating transcription in a stage-specific manner. Consistent …

The Caenorhabditis Elegans Heterochronic Gene Pathway Controls Stage-Specific Transcription Of Collagen Genes, Zhongchi Liu, Susan Kirch, Victor Ambros

Victor R. Ambros

In Caenorhabditis elegans, the terminal differentiation of the hypodermal cells occurs at the larval-to-adult molt, and is characterized in part by the formation of a morphologically distinct adult cuticle. The timing of this event is controlled by a pathway of heterochronic genes that includes the relatively direct regulatory gene, lin-29, and upstream genes lin-4, lin-14 and lin-28. Using northern analysis to detect endogenous collagen mRNA levels and collagen/lacZ reporter constructs to monitor collagen transcriptional activity, we show that the stage-specific switch from larval cuticle to adult cuticle correlates with the transcriptional activation of adult-specific collagen genes and repression of larval-specific …

Thermodynamics Of Charged Oligopeptide-Heparin Interactions., David Mascotti, Timothy Lohman

David P. Mascotti

No abstract provided.

Pollination Of The Crown Imperial Fritillaria Imperialis By Great Tits Parus Major, Winfried S. Peters, Michael Pirl, Gerhard Gottsberger, Dieter Stefan Peters

Winfried S. Peters

Formation Of The Isocyclic Ring Of Chlorophyll By Isolated Clamydomonas Reinhardtii Chloroplasts, David Bollivar, Samuel I. Beale

David Bollivar

Chlamydomonas reinhardtii chloroplasts catalyzed two sequential steps of Chl biosynthesis, S-adenosyl-L-methionine:Mg-protoporphyrin IX methyltransferase and Mg-protoporphyrin IX monomethyl ester oxidative cyclase. A double mutant strain of C. reinhardtii was constructed which has a cell wall deficiency and is unable to form chlorophyll in the dark. Dark-grown cells were disrupted with a BioNeb nebulizer under conditions which lysed the plasma membrane but not the chloroplast envelope. Chloroplasts were purified by Percoll density gradient centrifugation. The purified chloroplasts were used to define components required for the biosynthesis of Mg-2,4-divinylpheoporphyrin a 5 (divinyl protochlorophyllide) from Mg-protoporphyrin IX. Product formation requires the addition of Mg-protoporphyrin …

Regulation Of Iron Metabolism: Translational Effects Mediated By Iron, Heme, And Cytokines, David Mascotti, Diane Rup, Robert Thach

David P. Mascotti

No abstract provided.

Darwinism Evolving: Systems Dynamics And The Genealogy Of Natural Selection, David Depew, Bruce Weber

David J Depew

Darwinism Evolving examines the Darwinian research tradition in evolutionary biology from its inception to its turbulent present, arguing that recent advances in modeling the nonlinear dynamics of complex systems may well catalyze the next major phase of Darwinian evolutionism.While Darwinism has successfully resisted reduction to physics, the authors point out that it has from the outset developed and applied its core explanatory concept, natural selection, by borrowing models from dynamics, a branch of physics. The recent development of complex systems dynamics may afford Darwinism yet another occasion to expand its explanatory power.Darwinism's use of dynamical models has received insufficient attention …

Spontaneous Mutation During The Sexual Cycle Of Neurospora Crassa, Michael Watters, David Stadler

Michael Watters

The DNA sequences of 42 spontaneous mutations of the mtr gene in Neurospora crassa have been determined. The mutantws ere selected among sexual spores to represent mutations arising in the sexual cycle. Three sexualcycle-specific mutational classes are described: hotspot mutants, spontaneous repeatinduced point mutation (RIPS) and mutations occurring during a mutagenic phase of the sexual cycle. Together, these three sexual-cycle-specific mutational classes account fo5r0 % of the mutations in the sexual-cycle mutational spectrum. One thiordf all mutations occurred at onoef two mutational hotspots that predominantly produced tandem duplications of varying lengths with short repeats at their endpoints. Neither of the …

Hydraulic Conductivity Of Concentric Root Tissues Of Agave Deserti Englem. Under Wet And Drying Conditions, Gretchen North, P. Nobel

Gretchen North

Water moves from the root surface to the root xylem through a series of tissues, each with properties that influence the root radial hydraulic conductivity (LR). To determine LR for intact roots, root hydraulic conductivity (LP) and axial (xylem) conductance (Kh) were measured for root segments of the desert succulent Agave deserti Engelm. As layers were successively removed, LR was calculated for each layer by considering the conductivities in series. For the distal root region, no single tissue limited LR under wet conditions, although the suberized exodermis and sclerenchyma/endodermis were more limiting per cross-sectional area of the root than were …

Evolution, Ethics, And The Complexity Revolution, David Depew, Bruce Weber

David J Depew

No abstract provided.

A Beta-Linked Mannan Inhibits Adherence Of Pseudomonas Aeruginosa To Human Lung Epithelial Cells, Ali Azghani, Izola Williams, David B. Holiday, Alice R. Johnson

Ali Azghani