1gao
From Proteopedia
CRYSTAL STRUCTURE OF THE L44S MUTANT OF FERREDOXIN I
Overview
The reduction potential (E(0)') of the [4Fe-4S](2+/+) cluster of Azotobacter vinelandii ferredoxin I (AvFdI) and related ferredoxins is approximately 200 mV more negative than the corresponding clusters of Peptostreptococcus asaccharolyticus ferredoxin and related ferredoxins. Previous studies have shown that these differences in E(0)' do not result from the presence or absence of negatively charged surface residues or in differences in the types of hydrophobic residues found close to the [4Fe-4S](2+/+) clusters. Recently, a third, quite distinct class of ferredoxins (represented by the structurally characterized Chromatium vinosum ferredoxin) was shown to have a [4Fe-4S](2+/+) cluster with a very negative E(0)' similar to that of AvFdI. The observation that the sequences and structures surrounding the very negative E(0)' clusters in quite dissimilar proteins were almost identical inspired the construction of three additional mutations in the region of the [4Fe-4S](2+/+) cluster of AvFdI. The three mutations, V19E, P47S, and L44S, that incorporated residues found in the higher E(0)' P. asaccharolyticus ferredoxin all led to increases in E(0)' for a total of 130 mV with a 94-mV increase in the case of L44S. The results are interpreted in terms of x-ray structures of the FdI variants and show that the major determinant for the large increase in L44S is the introduction of an OH-S bond between the introduced Ser side chain and the Sgamma atom of Cys ligand 42 and an accompanying movement of water.
About this Structure
1GAO is a Single protein structure of sequence from Azotobacter vinelandii. Full crystallographic information is available from OCA.
Reference
Azotobacter vinelandii ferredoxin I: a sequence and structure comparison approach to alteration of [4Fe-4S]2+/+ reduction potential., Chen K, Jung YS, Bonagura CA, Tilley GJ, Prasad GS, Sridhar V, Armstrong FA, Stout CD, Burgess BK, J Biol Chem. 2002 Feb 15;277(7):5603-10. Epub 2001 Nov 9. PMID:11704670 Page seeded by OCA on Fri May 2 17:21:23 2008
