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Crystal Structures of Cystathionine β‑Synthase from Saccharomyces cerevisiae: One Enzymatic Step at a Time
Version 2 2018-04-16, 12:20
Version 1 2018-04-13, 19:35
journal contribution
posted on 2018-04-09, 00:00 authored by Yupeng Tu, Cheryl A. Kreinbring, Megan Hill, Cynthia Liu, Gregory A. Petsko, Christopher D. McCune, David B. Berkowitz, Dali Liu, Dagmar RingeCystathionine β-synthase
(CBS) is a key regulator of sulfur
amino acid metabolism, taking homocysteine from the methionine cycle
to the biosynthesis of cysteine via the trans-sulfuration pathway.
CBS is also a predominant source of H2S biogenesis. Roles
for CBS have been reported for neuronal death pursuant to cerebral
ischemia, promoting ovarian tumor growth, and maintaining drug-resistant
phenotype by controlling redox behavior and regulating mitochondrial
bioenergetics. The trans-sulfuration pathway is well-conserved in
eukaryotes, but the analogous enzymes have different enzymatic behavior
in different organisms. CBSs from the higher organisms contain a heme
in an N-terminal domain. Though the presence of the heme, whose functions
in CBSs have yet to be elucidated, is biochemically interesting, it
hampers UV–vis absorption spectroscopy investigations of pyridoxal
5′-phosphate (PLP) species. CBS from Saccharomyces
cerevisiae (yCBS) naturally lacks the heme-containing
N-terminal domain, which makes it an ideal model for spectroscopic
studies of the enzymological reaction catalyzed and allows structural
studies of the basic yCBS catalytic core (yCBS-cc). Here we present
the crystal structure of yCBS-cc, solved to 1.5 Å. Crystal structures
of yCBS-cc in complex with enzymatic reaction intermediates have been
captured, providing a structural basis for residues involved in catalysis.
Finally, the structure of the yCBS-cc cofactor complex generated by
incubation with an inhibitor shows apparent off-pathway chemistry
not normally seen with CBS.