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Structure-based mechanism for early PLP-mediated steps of rabbit cytosolic serine hydroxymethyltransferase reaction.
Biomed Res Int. 2013; 2013:458571.BR

Abstract

Serine hydroxymethyltransferase catalyzes the reversible interconversion of L-serine and glycine with transfer of one-carbon groups to and from tetrahydrofolate. Active site residue Thr254 is known to be involved in the transaldimination reaction, a crucial step in the catalytic mechanism of all pyridoxal 5'-phosphate- (PLP-) dependent enzymes, which determines binding of substrates and release of products. In order to better understand the role of Thr254, we have expressed, characterized, and determined the crystal structures of rabbit cytosolic serine hydroxymethyltransferase T254A and T254C mutant forms, in the absence and presence of substrates. These mutants accumulate a kinetically stable gem-diamine intermediate, and their crystal structures show differences in the active site with respect to wild type. The kinetic and crystallographic data acquired with mutant enzymes permit us to infer that conversion of gem-diamine to external aldimine is significantly slowed because intermediates are trapped into an anomalous position by a misorientation of the PLP ring, and a new energy barrier hampers the transaldimination reaction. This barrier likely arises from the loss of the stabilizing hydrogen bond between the hydroxymethyl group of Thr254 and the ε -amino group of active site Lys257, which stabilizes the external aldimine intermediate in wild type SHMTs.

Authors+Show Affiliations

Dipartimento di Scienze Biochimiche, Sapienza Università di Roma, 00185 Roma, Italy. martino.disalvo@uniroma1.itNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

23956983

Citation

Di Salvo, Martino L., et al. "Structure-based Mechanism for Early PLP-mediated Steps of Rabbit Cytosolic Serine Hydroxymethyltransferase Reaction." BioMed Research International, vol. 2013, 2013, p. 458571.
Di Salvo ML, Scarsdale JN, Kazanina G, et al. Structure-based mechanism for early PLP-mediated steps of rabbit cytosolic serine hydroxymethyltransferase reaction. Biomed Res Int. 2013;2013:458571.
Di Salvo, M. L., Scarsdale, J. N., Kazanina, G., Contestabile, R., Schirch, V., & Wright, H. T. (2013). Structure-based mechanism for early PLP-mediated steps of rabbit cytosolic serine hydroxymethyltransferase reaction. BioMed Research International, 2013, 458571. https://doi.org/10.1155/2013/458571
Di Salvo ML, et al. Structure-based Mechanism for Early PLP-mediated Steps of Rabbit Cytosolic Serine Hydroxymethyltransferase Reaction. Biomed Res Int. 2013;2013:458571. PubMed PMID: 23956983.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Structure-based mechanism for early PLP-mediated steps of rabbit cytosolic serine hydroxymethyltransferase reaction. AU - Di Salvo,Martino L, AU - Scarsdale,J Neel, AU - Kazanina,Galina, AU - Contestabile,Roberto, AU - Schirch,Verne, AU - Wright,H Tonie, Y1 - 2013/07/15/ PY - 2013/06/06/received PY - 2013/06/26/accepted PY - 2013/8/20/entrez PY - 2013/8/21/pubmed PY - 2014/4/8/medline SP - 458571 EP - 458571 JF - BioMed research international JO - Biomed Res Int VL - 2013 N2 - Serine hydroxymethyltransferase catalyzes the reversible interconversion of L-serine and glycine with transfer of one-carbon groups to and from tetrahydrofolate. Active site residue Thr254 is known to be involved in the transaldimination reaction, a crucial step in the catalytic mechanism of all pyridoxal 5'-phosphate- (PLP-) dependent enzymes, which determines binding of substrates and release of products. In order to better understand the role of Thr254, we have expressed, characterized, and determined the crystal structures of rabbit cytosolic serine hydroxymethyltransferase T254A and T254C mutant forms, in the absence and presence of substrates. These mutants accumulate a kinetically stable gem-diamine intermediate, and their crystal structures show differences in the active site with respect to wild type. The kinetic and crystallographic data acquired with mutant enzymes permit us to infer that conversion of gem-diamine to external aldimine is significantly slowed because intermediates are trapped into an anomalous position by a misorientation of the PLP ring, and a new energy barrier hampers the transaldimination reaction. This barrier likely arises from the loss of the stabilizing hydrogen bond between the hydroxymethyl group of Thr254 and the ε -amino group of active site Lys257, which stabilizes the external aldimine intermediate in wild type SHMTs. SN - 2314-6141 UR - https://www.unboundmedicine.com/medline/citation/23956983/Structure_based_mechanism_for_early_PLP_mediated_steps_of_rabbit_cytosolic_serine_hydroxymethyltransferase_reaction_ L2 - https://doi.org/10.1155/2013/458571 DB - PRIME DP - Unbound Medicine ER -