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Structure of soybean serine acetyltransferase and formation of the cysteine regulatory complex as a molecular chaperone.

DIR@IMTECH: CSIR-Institute of Microbial Technology

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Title Structure of soybean serine acetyltransferase and formation of the cysteine regulatory complex as a molecular chaperone.
 
Creator Yi, Hankuil
Dey, Sanghamitra
Kumaran, Sangaralingam
Lee, Soon Goo
Krishnan, Hari B
Jez, Joseph M
 
Description Serine acetyltransferase (SAT) catalyzes the limiting reaction in plant and microbial biosynthesis of cysteine. In addition to its enzymatic function, SAT forms a macromolecular complex with O-acetylserine sulfhydrylase. Formation of the cysteine regulatory complex (CRC) is a critical biochemical control feature in plant sulfur metabolism. Here we present the 1.75-3.0 Å resolution x-ray crystal structures of soybean (Glycine max) SAT (GmSAT) in apoenzyme, serine-bound, and CoA-bound forms. The GmSAT-serine and GmSAT-CoA structures provide new details on substrate interactions in the active site. The crystal structures and analysis of site-directed mutants suggest that His(169) and Asp(154) form a catalytic dyad for general base catalysis and that His(189) may stabilize the oxyanion reaction intermediate. Glu(177) helps to position Arg(203) and His(204) and the β1c-β2c loop for serine binding. A similar role for ionic interactions formed by Lys(230) is required for CoA binding. The GmSAT structures also identify Arg(253) as important for the enhanced catalytic efficiency of SAT in the CRC and suggest that movement of the residue may stabilize CoA binding in the macromolecular complex. Differences in the effect of cold on GmSAT activity in the isolated enzyme versus the enzyme in the CRC were also observed. A role for CRC formation as a molecular chaperone to maintain SAT activity in response to an environmental stress is proposed for this multienzyme complex in plants.
 
Publisher Baltimore, MD : American Society for Biochemistry and Molecular Biology
 
Date 2013-12-20
 
Type Article
PeerReviewed
 
Relation http://www.jbc.org/content/288/51/36463.long
http://crdd.osdd.net/open/1607/
 
Identifier Yi, Hankuil and Dey, Sanghamitra and Kumaran, Sangaralingam and Lee, Soon Goo and Krishnan, Hari B and Jez, Joseph M (2013) Structure of soybean serine acetyltransferase and formation of the cysteine regulatory complex as a molecular chaperone. The Journal of biological chemistry, 288 (51). pp. 36463-72. ISSN 1083-351X