title: Identification, characterization, and structure/function analysis of a corrin reductase involved in adenosylcobalamin biosynthesis.
abstract: Vitamin B(12), the antipernicious anemia factor, is the cyano derivative of adenosylcobalamin, which is one of nature's most complex coenzymes. Adenosylcobalamin is made along one of two similar yet distinct metabolic pathways, which are referred to as the aerobic and anaerobic routes. The aerobic pathway for cobalamin biosynthesis proceeds via cobalt insertion into a ring-contracted macrocycle, which is closely followed by adenosylation of the cobalt ion. An important prerequisite for adenosylation is the reduction of the centrally chelated metal from Co(II) to a highly nucleophilic Co(I) form. We have cloned a gene, cobR, encoding a biosynthetic enzyme with this co(II)rrin reductase activity from Brucella melitensis. The protein has been overproduced, and the resulting flavoprotein has been purified, characterized, and crystallized and its structure determined to 1.6A resolution. Kinetic and EPR analysis reveals that the enzyme proceeds via a semiquinone form. It is proposed that CobR may interact with the adenosyltransferase to overcome the large thermodynamic barrier required for co(II)rrin reduction.
authors.affiliation: Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Lawrence
authors.forename: Evelyne
authors.initials: E
authors.lastname: Deery
authors.forename: Kirsty J
authors.initials: KJ
authors.lastname: McLean
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Munro
authors.forename: Richard W
authors.initials: RW
authors.lastname: Pickersgill
authors.forename: Stephen E J
authors.initials: SE
authors.lastname: Rigby
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Warren
mesh_terms: D017347:Brucella melitensis / Q000201:enzymology; D003001:Cloning, Molecular; D003035:Cobalt / Q000737:chemistry; D003038:Cobamides / Q000096:biosynthesis*; D045728:Corrinoids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D007477:Ions; D007700:Kinetics; D008956:Models, Chemical; D008968:Molecular Conformation; D010088:Oxidoreductases / Q000737:chemistry* / Q000502:physiology; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014805:Vitamin B 12 / Q000737:chemistry
chemical_list: D003038:Cobamides; D045728:Corrinoids; D007477:Ions; C473700:corrin; D003035:Cobalt; D010088:Oxidoreductases; C529270:corrin reductase, Brucella melitensis; C000913:cobamamide; D014805:Vitamin B 12