The critical role of a conserved lysine residue in periplasmic nitrate reductase catalyzed reactions.

Autor: Giri NC; Department of Chemistry and Chemical Biology, Indiana University Indianapolis, Indianapolis, IN, USA., Mintmier B; Department of Chemistry and Chemical Biology, Indiana University Indianapolis, Indianapolis, IN, USA., Radhakrishnan M; Department of Chemistry and Chemical Biology, Indiana University Indianapolis, Indianapolis, IN, USA., Mielke JW; Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA., Wilcoxen J; Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI, USA. jarettw@uwm.edu., Basu P; Department of Chemistry and Chemical Biology, Indiana University Indianapolis, Indianapolis, IN, USA. basup@iu.edu.
Jazyk: angličtina
Zdroj: Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry [J Biol Inorg Chem] 2024 Jun; Vol. 29 (4), pp. 395-405. Date of Electronic Publication: 2024 May 23.
DOI: 10.1007/s00775-024-02057-x
Abstrakt: Periplasmic nitrate reductase NapA from Campylobacter jejuni (C. jejuni) contains a molybdenum cofactor (Moco) and a 4Fe-4S cluster and catalyzes the reduction of nitrate to nitrite. The reducing equivalent required for the catalysis is transferred from NapC → NapB → NapA. The electron transfer from NapB to NapA occurs through the 4Fe-4S cluster in NapA. C. jejuni NapA has a conserved lysine (K79) between the Mo-cofactor and the 4Fe-4S cluster. K79 forms H-bonding interactions with the 4Fe-4S cluster and connects the latter with the Moco via an H-bonding network. Thus, it is conceivable that K79 could play an important role in the intramolecular electron transfer and the catalytic activity of NapA. In the present study, we show that the mutation of K79 to Ala leads to an almost complete loss of activity, suggesting its role in catalytic activity. The inhibition of C. jejuni NapA by cyanide, thiocyanate, and azide has also been investigated. The inhibition studies indicate that cyanide inhibits NapA in a non-competitive manner, while thiocyanate and azide inhibit NapA in an uncompetitive manner. Neither inhibition mechanism involves direct binding of the inhibitor to the Mo-center. These results have been discussed in the context of the loss of catalytic activity of NapA K79A variant and a possible anion binding site in NapA has been proposed.
(© 2024. The Author(s), under exclusive licence to Society for Biological Inorganic Chemistry (SBIC).)
Databáze: MEDLINE
Externí odkaz: