Related Experiment Video
Updated: Oct 17, 2026

Functional Site-Directed Fluorometry in Native Cells to Study Skeletal Muscle Excitability
Published on: June 2, 2023
Mutation of the surface valine residues 8 and 44 in the rubredoxin from Clostridium pasteurianum: solvent access
1School of Chemistry, University of Melbourne, Parkville, Victoria, Australia.
Abstract:
The Pr(i) sidechains of two adjacent valine residues, V8 and V44, define the surface of the rubredoxin from Clostridium pasteurianum and control access to its Fe(S-Cys)4 active site. To assess the effect of systematic change of the steric bulk of the alkyl sidechains, eight single and three double mutant proteins have been isolated which vary G (H), A (Me), V (Pr(i)), L (Bu(i)) and I (Bu(s)) at those positions. X-ray crystal structures of the Fe(III) forms of the V44A and V44I proteins are reported. Positive shifts in reversible potential of up to 116 mV are observed and attributed to increased polarity around the Fe(S-Cys)4 site induced by (1) changes in protein backbone conformation driven by variation of the steric demands of the sidechain substituents and (2) changes in solvent access to the side-chains of ligands C9 and C42. Data for the V44A mutant show that a minor change in the steric requirements of a surface residue can introduce a NH...Sgamma hydrogen bond at the active site and lead to a shift in potential of + 50 mV.
Related Concept Videos
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein.
Ligand Binding and Linkage
Protein Modifications in the RER
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Gene Families
Occasionally these regions can be adapted to take on new roles within the organism, becoming novel genes...
Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...
