1B0V

I40N MUTANT OF AZOTOBACTER VINELANDII FDI

Summary for 1B0V

• Entry DOI: 10.2210/pdb1b0v/pdb
• Descriptor: PROTEIN (FERREDOXIN), IRON/SULFUR CLUSTER, FE3-S4 CLUSTER (3 entities in total)
• Functional Keywords: iron-sulfur, electron transport
• Biological source: Azotobacter vinelandii
• Total number of polymer chains: 4
• Total formula weight: 50831.64

Authors

Sridhar, V.,Prasad, G.S.,Stout, C.D.,Chen, K.,Burgess, B.K. (deposition date: 1998-11-12, release date: 2000-01-19, Last modification date: 2023-08-09)

Primary citation

Chen, K.,Tilley, G.J.,Sridhar, V.,Prasad, G.S.,Stout, C.D.,Armstrong, F.A.,Burgess, B.K.
Alteration of the reduction potential of the [4Fe-4S](2+/+) cluster of Azotobacter vinelandii ferredoxin I.
J.Biol.Chem., 274:36479-36487, 1999

PubMed Abstract: The [4Fe-4S](2+/+) cluster of Azotobacter vinelandii ferredoxin I (FdI) has an unusually low reduction potential (E(0')) relative to other structurally similar ferredoxins. Previous attempts to raise that E(0') by modification of surface charged residues were unsuccessful. In this study mutants were designed to alter the E(0') by substitution of polar residues for nonpolar residues near the cluster and by modification of backbone amides. Three FdI variants, P21G, I40N, and I40Q, were purified and characterized, and electrochemical E(0') measurements show that all had altered E(0') relative to native FdI. For P21G FdI and I40Q FdI, the E(0') increased by +42 and +53 mV, respectively validating the importance of dipole orientation in control of E(0'). Protein Dipole Langevin Dipole calculations based on models for those variants accurately predicted the direction of the change in E(0') while overestimating the magnitude. For I40N FdI, initial calculations based on the model predicted a +168 mV change in E(0') while a -33 mV change was observed. The x-ray structure of that variant, which was determined to 2.8 A, revealed a number of changes in backbone and side chain dipole orientation and in solvent accessibility, that were not predicted by the model and that were likely to influence E(0'). Subsequent Protein Dipole Langevin Dipole calculations (using the actual I40N x-ray structures) did quite accurately predict the observed change in E(0').

PubMed: 10593945
DOI: 10.1074/jbc.274.51.36479

Experimental method

X-RAY DIFFRACTION (2.8 Å)