Work

Probing the Catalytic Charge-Relay System in Alanine Racemase with Genetically Encoded Histidine Mimetics

Year: 2016

Type: article

Abstract: Histidine is a unique amino acid with an imidazole side chain in which both of the nitrogen atoms are capable of serving as a proton donor and proton acceptor in hydrogen bonding interactions. In order to probe the functional role of histidine involved in hydrogen bonding networks, fine-tuning the hydrogen bonding potential of the imidazole side chain is required but not feasible through traditional mutagenesis methods. Here, we show that two close mimetics of histidine, 3-methyl-histidine and thiazole alanine, can be genetically encoded using engineered pyrrolysine incorporation machinery. Replacement of the three histidine residues predicted to be involved in an extended charge-relay system in alanine racemase with 3-methyl-histidine or thiazole alanine shows a dramatic loss in the enzyme's catalytic efficiency, implying the role of this extended charge-relay system in activating the active site residue Y265, a general acid/base catalyst in the enzyme.

Source: ACS Chemical Biology

DOI: 10.1021/acschembio.6b00940

Authors: Vangmayee Sharma, Yane-Shih Wang, Wenshe R. Liu

Institution: Texas A&M University

Language: English

Topic: Amino Acid Enzymes and Metabolism

Subfield: Biochemistry

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: green

Funders: Welch Foundation, National Cancer Institute, National Institute of General Medical Sciences

Awards: Phage Display with Two Genetically Incorporated Noncanonical Amino Acids, G6553094674, Studying Reversible Histone Acylations in Nucleosome Contexts