Synthesis and characterization of homochiral polymeric S-malato molybdate(VI): toward the potentially stereospecific formation and absolute configuration of iron-molybdenum cofactor in nitrogenase.
Reaction of sodium or potassium molybdate and excess malic acid in a wide range of pH values (pH 4.0-7.0) resulted in the isolation of two cis-dioxo-bis(malato)-Mo(VI) complexes, viz. Na(3)[MoO(2)H(S-mal)(2)] and K(3)[MoO(2)H(S-mal)(2)].H(2)O (H(3)mal=malic acid). The sodium complex is also characterized by an X-ray structure analysis, showing that the mononuclear Mo units are linked together via very strong symmetric CO(2)...H... O(2)C-hydrogen bond [2.432(5) A], forming a polymeric chain. The molybdenum atoms are quasi-octahedrally coordinated by two cis-oxo groups and two bidentate malate ligands via its alkoxy and alpha-carboxyl groups, while the beta-carboxylic and carboxylate groups remain uncomplexed, as the coordination of vicinal carboxylate and alkoxide of homocitrate in FeMo cofactor of nitrogenase. The absolute configuration of the metal center in this S-malato complex is assigned as Lambda and the homochirality within the chain is established as a homochiral form ...Lambda(S)-Lambda(S)-Lambda(S)-Lambda(S)... . It is proposed that the chiral configuration of the metal center in wild-type FeMo-co biosynthesis might be induced by the early coordination of the chiral R-homocitric acid, while a mixture of raceme might be obtained in the biosynthesis of NifV(-) FeMo-cofactor. The absolute configuration of wild-type FeMo-cofactor is assigned as Delta(R).
Zhou
Zhao-Hui
ZH
Department of Chemistry and State Key Laboratory for Physical Chemistry of Solid Surface, Xiamen University, Xiamen 361005, China. zhzhou@xmu.edu.cn
Yan
Wen-Bin
WB
Wan
Hui-Lin
HL
Tsai
Khi-Rui
KR
D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008293:Malates / Q000737:chemistry; D008982:Molybdenum / Q000737:chemistry*; D008983:Molybdoferredoxin / Q000737:chemistry*; D009591:Nitrogenase / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism
D008293:Malates; D008983:Molybdoferredoxin; D009942:Organometallic Compounds; D011108:Polymers; C030298:malic acid; D008982:Molybdenum; D009591:Nitrogenase