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B6db references: 28126739

type Journal Article
authors Dharavath S, Raj I, Gourinath S
title Structure-based mutational studies of O-acetylserine sulfhydrylase reveal the reason for the loss of cysteine synthase complex formation in Brucella abortus
journal Biochem J
sel selected
ui 28126739
year (2017)
volume 474
number 7
pages 1221-1239
keywords O-acetyl serine sulfydrylase; active site; cysteine synthase complex; protein–protein interactions
abstract Cysteine biosynthesis takes place via a two-step pathway in bacteria, fungi, plants and protozoan parasites, but not in humans, and hence, the machinery of cysteine biosynthesis is an opportune target for therapeutics. The decameric cysteine synthase complex (CSC) is formed when the C-terminal tail of serine acetyltransferase (SAT) binds in the active site of O-acetylserine sulfydrylase (OASS), playing a role in the regulation of this pathway. Here, we show that OASS from Brucella abortus (BaOASS) does not interact with its cognate SAT C-terminal tail. Crystal structures of native BaOASS showed that residues Gln96 and Tyr125 occupy the active-site pocket and interfere with the entry of the SAT C-terminal tail. The BaOASS (Q96A-Y125A) mutant showed relatively strong binding (Kd = 32.4 μM) to BaSAT C-terminal peptides in comparison with native BaOASS. The mutant structure looks similar except that the active-site pocket has enough space to bind the SAT C-terminal end. Surface plasmon resonance results showed a relatively strong (7.3 μM Kd) interaction between BaSAT and the BaOASS (Q96A-Y125A), but no interaction with native BaOASS. Taken together, our observations suggest that the CSC does not form in B. abortus.
last changed 2017/08/07 12:03

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