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Erika A. Taylor, Ph.D.

Articles 1 - 5 of 5

Full-Text Articles in Physical Sciences and Mathematics

Improving Alternate Lignin Catabolite Utilization Of Ligab From Sphingobium Sp. Strain Syk-6 Through Site Directed Mutagenesis, Kevin P. Barry, Erin F. Cohn, Abraham Ngu, Erika A. Taylor Jun 2015

Improving Alternate Lignin Catabolite Utilization Of Ligab From Sphingobium Sp. Strain Syk-6 Through Site Directed Mutagenesis, Kevin P. Barry, Erin F. Cohn, Abraham Ngu, Erika A. Taylor

Erika A. Taylor, Ph.D.

Protocatechuate 4,5-dioxygenase (LigAB) catalyzes dioxygenation of multiple lignin derived aromatic compounds—such as protocatechuate (PCA), gallate (GA) and 3-O-methyl gallate (3OMG)—with decreasing proficiency as the molecule size increases. We predicted that phenylalanine-103 of the α subunit (Phe103α) controls substrate specificity through interaction with the C5-funtionality of bound substrates, and mutagenesis would enhance GA and 3OMG catalysis. LigAB with Phe103α mutations (F103 V, F103T and F103H) displayed enhanced catalytic efficiency for dioxygenation of 3OMG, with mutants displaying 12- to 31-fold increases in View the MathML source, making these mutant enzymes more active with 3OMG than its native dioxygenase (DesZ). The F103T and …

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Sucralose Destabilization Of Protein Structure, Lee Chen, Nimesh Shukla, Inha Cho, Erin F. Cohn, Erika A. Taylor, Christina M. Othon Mar 2015

Sucralose Destabilization Of Protein Structure, Lee Chen, Nimesh Shukla, Inha Cho, Erin F. Cohn, Erika A. Taylor, Christina M. Othon

Erika A. Taylor, Ph.D.

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. The presence of sucralose in solution is found to destabilize the native structure of two model protein systems: the globular protein bovine serum albumin and an enzyme staphylococcal nuclease. The melting temperature of these proteins decreases as a linear function of sucralose concentration. We correlate this destabilization to the increased polarity of the molecule. The strongly polar nature is manifested as a large dielectric friction exerted on the excited-state rotational diffusion of tryptophan using time-resolved fluorescence …

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Characterizing The Promiscuity Of Ligab, A Lignin Catabolite Degrading Extradiol Dioxygenase From Sphingomonas Paucimobilis Syk-6, Kevin P. Barry, Erika A. Taylor Sep 2013

Characterizing The Promiscuity Of Ligab, A Lignin Catabolite Degrading Extradiol Dioxygenase From Sphingomonas Paucimobilis Syk-6, Kevin P. Barry, Erika A. Taylor

Erika A. Taylor, Ph.D.

LigAB from Sphingomonas paucimobilis SYK-6 is the only structurally characterized dioxygenase of the largely uncharacterized superfamily of Type II extradiol dioxygenases (EDO). This enzyme catalyzes the oxidative ring-opening of protocatechuate (3,4-dihydroxybenzoic acid or PCA) in a pathway allowing the degradation of lignin derived aromatic compounds (LDACs). LigAB has also been shown to utilize two other LDACs from the same metabolic pathway as substrates, gallate, and 3-O-methyl gallate; however, kcat/KM had not been reported for any of these compounds. In order to assess the catalytic efficiency and get insights into the observed promiscuity of this enzyme, steady-state kinetic analyses were performed …

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Escherichia Coli Heptosyltransferase I: Investigation Of Protein Dynamics Of A Gt-B Structural Enzyme, Erika A. Taylor, Daniel J. Czyzyk, Shreya S. Sawant, Carlos A. Ramirez-Mondragon Aug 2013

Escherichia Coli Heptosyltransferase I: Investigation Of Protein Dynamics Of A Gt-B Structural Enzyme, Erika A. Taylor, Daniel J. Czyzyk, Shreya S. Sawant, Carlos A. Ramirez-Mondragon

Erika A. Taylor, Ph.D.

Heptosyltransferase I (HepI), the enzyme responsible for the transfer of l-glycero-d-manno-heptose to a 3-deoxy-α-d-manno-oct-2-ulopyranosonic acid (Kdo) of the growing core region of lipopolysaccharide, is a member of the GT-B structural class of enzymes. Crystal structures have revealed open and closed conformations of apo and ligand-bound GT-B enzymes, implying that large-scale protein conformational dynamics play a role in their reaction mechanism. Here we report transient kinetic analysis of conformational changes in HepI reported by intrinsic tryptophan fluorescence and present the first real-time evidence of a GT-B enzyme undergoing a substrate binding-induced transition from an open to closed state prior to catalysis.

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Second-Sphere Amino Acids Contribute To Transition-State Structure In Bovine Purine Nucleoside Phosphorylase, Lei Li, Minkui Luo, Mahmoud Ghanem, Erika A. Taylor, Vern L. Schramm Feb 2008

Second-Sphere Amino Acids Contribute To Transition-State Structure In Bovine Purine Nucleoside Phosphorylase, Lei Li, Minkui Luo, Mahmoud Ghanem, Erika A. Taylor, Vern L. Schramm

Erika A. Taylor, Ph.D.

Transition-state structures of human and bovine of purine nucleoside phosphorylases differ, despite 87% homologous amino acid sequences. Human PNP (HsPNP) has a fully dissociated transition state, while that for bovine PNP (BtPNP) has early SN1 character. Crystal structures and sequence alignment indicate that the active sites of these enzymes are the same within crystallographic analysis, but residues in the second-sphere from the active sites differ significantly. Residues in BtPNP have been mutated toward HsPNP, resulting in double (Asn123Lys; Arg210Gln) and triple mutant PNPs (Val39Thr; Asn123Lys; Arg210Gln). Steady-state kinetic studies indicated unchanged catalytic activity, while pre-steady-state studies indicate that the chemical …

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