ISSN:
1572-8862
Keywords:
Nitrogenase MoFe-protein
;
M-cluster cage
;
molecular-sieve effects
;
substrates binding modes
;
homocitrate-mediated proton-transport relay
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Abstract It A proposed that the M-cluster cage (Kim-Rees model) in active N2-ase can exert shape-selective “molecular-sieve” effects in molecular recognition of exogenous substrates, by providing inside multinuclear active-sites the cavity for N2, C2H2, cyclopropene, and N2O reduction, with [Mo-3Fe]-site available only for N2 reduction: on the other handn-RC— CH,n-RC— N,n-RN-C , C—N− and N3 −, are bound outside the cavity at the [2Fe]-site left by the labilizable ligand “Y”. A terminal carboxylate of the Mo-bound (R)-homocitrate is just in position to protect a H2-evolution site on the P-cluster pair from CO inhibition, and also to take part in mediating a P-cluster-to-Mo-site H+-relay system (involving two hydrogen-bonded H2O) specifically required for N. reduction. The nonreducibility of CO at the [Mo-3Fe]-site is also explained. Experimental support for molecular-sieve effects of M-cluster cage has been obtained from the observed decrease in ethene-cis-d: selectivity by competitive inhibition of HC—CH reduction in D2O by N—N.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01165769
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