Alkyne substrate interaction within the nitrogenase MoFe protein.

Alkyne substrate interaction within the nitrogenase MoFe protein. Research Abstract Details 

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Alkyne substrate interaction within the nitrogenase MoFe protein. Abstract Text:

Patricia C Dos Santos,Suzanne M Mayer,Brett M Barney,Lance C Seefeldt,Dennis R Dean,Patricia C Dos Santos,Suzanne M Mayer,Brett M Barney,Lance C Seefeldt,Dennis R Dean,Patricia C Dos Santos,Suzanne M Mayer,Brett M Barney,Lance C Seefeldt,Dennis R Dean,

Nitrogenase catalyzes the biological reduction of N(2) to ammonia (nitrogen fixation), as well as the two-electron reduction of the non-physiological alkyne substrate acetylene (HC identical withCH). A complex metallo-organic species called FeMo-cofactor provides the site of substrate reduction within the MoFe protein, but exactly where and how substrates interact with FeMo-cofactor remains unknown. Recent results have shown that the MoFe protein alpha-70(Val) residue, whose side chain approaches one Fe-S face of FeMo-cofactor, plays a significant role in defining substrate access to the active site. For example, substitution of alpha-70(Val) by alanine results in an increased capacity for the reduction of the larger alkyne propyne (HC identical withC-CH(3)), whereas, substitution by isoleucine at this position nearly eliminates the capacity for the reduction of acetylene. These and complementary spectroscopic studies led us to propose that binding of short chain alkynes occurs with side-on binding to Fe atom 6 within FeMo-cofactor. In the present work, the alpha-70(Val) residue was substituted by glycine and this MoFe protein variant shows an increased capacity for reduction of the terminal alkyne, 1-butyne (HC identical withC-CH(2)-CH(3)). This protein shows no detectable reduction of the internal alkyne 2-butyne (H(3)C-C identical withC-CH(3)). In contrast, substitution of the nearby alpha-191(Gln) residue by alanine, in combination with the alpha-70(Ala) substitution, does result in significant reduction of 2-butyne, with the exclusive product being 2-cis-butene. These results indicate that the reduction of alkynes by nitrogenases involves side-on binding of the alkyne to Fe6 within FeMo-cofactor, and that a terminal acidic proton is not required for reduction. The successful design of amino acid substitutions that permit the targeted accommodation of an alkyne that otherwise is not a nitrogenase substrate provides evidence to support the current model for alkyne interaction within the nitrogenase MoFe protein.

Alkyne substrate interaction within the nitrogenase MoFe protein. Publishing Authors By Initials

PC Dos Santos,SM Mayer,BM Barney,LC Seefeldt,DR Dean,PC Dos Santos,SM Mayer,BM Barney,LC Seefeldt,DR Dean,PC Dos Santos,SM Mayer,BM Barney,LC Seefeldt,DR Dean,

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Alkyne substrate interaction within the nitrogenase MoFe protein. Journal Published:

PUBLICATION TYPE: Journal Article

Journal: Journal of inorganic biochemistry

VOLUME: 101

Page Numbers: 1642-8

Journal Abbreviation: J. Inorg. Biochem.

ISSN: 0162-0134

DAY: 29

MONTH: 05

YEAR: 2007

Alkyne substrate interaction within the nitrogenase MoFe protein. Information

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LANGUAGE: eng

NlmUniqueID: 7905788

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Grant and Affiliation Information for Alkyne substrate interaction within the nitrogenase MoFe protein.

AFFILIATION: Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States.

Country: United States

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MEDLINETA: J Inorg Biochem

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