Previous studies have shown that the nifH gene product is required for FeMo cofactor biosynthesis and insertion and that a delta nifH strain of Azotobacter vinelandii designated DJ54 accumulates a FeMo cofactor-deficient MoFe protein that is distinct from the FeMo cofactor-deficient protein synthesis by Nif B-, N-, or E- strains [Tal, S., Chun, T., Gavini, N., & Burgess, B. K. (1991) J. Biol. Chem. 266, 10654-10657]. Here we report the purification and activation of the MoFe protein from DJ54. The purified protein is an alpha 2 beta 2 tetramer that is indistinguishable from the wild-type MoFe protein by the criteria of SDS-polyacrylamide gel electrophoresis, native gel electrophoresis, and two-dimensional gel electrophoresis. It binds normally to its redox partner, the Fe protein, by the criterion of chemical cross-linking. It does not contain FeMo cofactor and does not catalyze significant C2H2 reduction or reduction-independent MgATP hydrolysis. It can, however, be activated with FeMo cofactor following the addition of the Fe protein and MgATP when an additional required component(s) is supplied by cell-free extracts from a delta nifD strain of A. vinelandii. The purified DJ54 MoFe protein does contain P-clusters by the criteria of metal analysis, CD spectroscopy, cluster extrusion, and electrochemical reduction of the POX state. In the presence of dithionite it exhibits an axial S = 1/2 EPR signal that integrates to 0.1-0.3 spin per alpha 2 beta 2 tetramer.(ABSTRACT TRUNCATED AT 250 WORDS)
Peptidyl-prolyl cis/trans isomerases (PPIases) play a pivotal role in catalyzing the correct folding of many prokaryotic and eukaryotic proteins that are implicated in a variety of biological functions, ranging from cell cycle regulation to bacterial infection. The nif accessory protein NifM, which is essential for the biogenesis of a functional NifH component of nitrogenase, is a PPIase. To understand the nature of the molecular signature that defines the NifM dependence of NifH, we screened a library of nifH mutants in the nitrogen-fixing bacterium Azotobacter vinelandii for mutants that acquired NifM independence. Here, we report that NifH can acquire NifM independence when the conserved Pro258 located in the C-terminal region of NifH, which wraps around the other subunit in the NifH dimer, is replaced by serine.Peptidyl-prolyl cis/trans isomerases (PPIases) catalyze the cis/trans isomerization of the peptidyl-prolyl peptide bond in oligopeptides and proteins, a rate-limiting step in the process of protein folding that is essential for generating functional proteins (5-7). Some denatured proteins regain their native conformations within milliseconds to seconds, whereas others refold very slowly, with the time ranging from minutes to hours. The slow conformational changes arise from the wellknown delocalization of electrons in the amide bond and are even more pronounced if additional steric constraints are imposed by the proline ring. PPIases enhance the rate of refolding of the slowly folding forms of denatured proteins by catalyzing the cis/trans isomerization of these peptidyl-prolyl bonds (5,19
Summary Additional targeted research and customized training programs could spearhead strategies for elimination of the disparities in prevalence and control of high BP between African Americans and the remainder of the US general population.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.