title: Inter-domain communication of human cystathionine β-synthase: structural basis of S-adenosyl-L-methionine activation.
abstract: Cystathionine β-synthase (CBS) is a key enzyme in sulfur metabolism, and its inherited deficiency causes homocystinuria. Mammalian CBS is modulated by the binding of S-adenosyl-l-methionine (AdoMet) to its regulatory domain, which activates its catalytic domain. To investigate the underlying mechanism, we performed x-ray crystallography, mutagenesis, and mass spectrometry (MS) on human CBS. The 1.7 Å structure of a AdoMet-bound CBS regulatory domain shows one AdoMet molecule per monomer, at the interface between two constituent modules (CBS-1, CBS-2). AdoMet binding is accompanied by a reorientation between the two modules, relative to the AdoMet-free basal state, to form interactions with AdoMet via residues verified by mutagenesis to be important for AdoMet binding (Phe(443), Asp(444), Gln(445), and Asp(538)) and for AdoMet-driven inter-domain communication (Phe(443), Asp(538)). The observed structural change is further supported by ion mobility MS, showing that as-purified CBS exists in two conformational populations, which converged to one in the presence of AdoMet. We therefore propose that AdoMet-induced conformational change alters the interface and arrangement between the catalytic and regulatory domains within the CBS oligomer, thereby increasing the accessibility of the enzyme active site for catalysis.
authors.affiliation: From the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: McCorvie
authors.affiliation: From the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom.
authors.forename: Jolanta
authors.initials: J
authors.lastname: Kopec
authors.affiliation: Worldwide Research and Development, Pfizer Inc., Groton, Connecticut 06340, and.
authors.forename: Suk-Joon
authors.initials: SJ
authors.lastname: Hyung
authors.affiliation: From the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom.
authors.forename: Fiona
authors.initials: F
authors.lastname: Fitzpatrick
authors.affiliation: Worldwide Research and Development, Pfizer Inc., Groton, Connecticut 06340, and.
authors.forename: Xidong
authors.initials: X
authors.lastname: Feng
authors.affiliation: the Pfizer Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, Massachusetts 02140.
authors.forename: Daniel
authors.initials: D
authors.lastname: Termine
authors.affiliation: From the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom.
authors.forename: Claire
authors.initials: C
authors.lastname: Strain-Damerell
authors.affiliation: From the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom.
authors.forename: Melanie
authors.initials: M
authors.lastname: Vollmar
authors.affiliation: the Pfizer Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, Massachusetts 02140.
authors.forename: James
authors.initials: J
authors.lastname: Fleming
authors.affiliation: the Pfizer Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, Massachusetts 02140.
authors.forename: Jay M
authors.initials: JM
authors.lastname: Janz
authors.affiliation: the Pfizer Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, Massachusetts 02140 christine.bulawa@pfizer.com.
authors.forename: Christine
authors.initials: C
authors.lastname: Bulawa
authors.affiliation: From the Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, Oxford OX3 7DQ, United Kingdom, wyatt.yue@sgc.ox.ac.uk.
authors.forename: Wyatt W
authors.initials: WW
authors.lastname: Yue
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003541:Cystathionine beta-Synthase / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012436:S-Adenosylmethionine / Q000737:chemistry*
chemical_list: D012436:S-Adenosylmethionine; D003541:Cystathionine beta-Synthase
keywords: Activation; Allosteric Regulation; Conformational Change; Crystallography; Cystathionine β-Synthase; Enzyme; Mass Spectrometry (MS); S-adenosyl-l-methionine (AdoMet); SAM