1myg
From Proteopedia
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HIGH RESOLUTION X-RAY STRUCTURES OF PIG METMYOGLOBIN AND TWO CD3 MUTANTS MB(LYS45-> ARG) AND MB(LYS45-> SER)
Overview
The structure of pig aquometmyoglobin has been refined to a, crystallographic R-factor of 19.8% against X-ray diffraction data between, 10- and 1.75-A spacing. The final structural model comprises two molecules, of pig myoglobin, 233 water molecules, and two sulfate ions. A water, molecule is coordinated to each of the heme iron atoms with an average, Fe-OH2 bond distance of 2.19 A, and the mean Fe-N epsilon (proximal, histidine-93) distance is 2.20 A. In contrast to the structure of sperm, whale metmyoglobin, the iron is not significantly displaced from the plane, of the heme. At the entrance to the heme pocket, the side-chain amino, group of lysine-45 (CD3) is well-defined in the electron density map and, forms salt-bridging interactions with the heme 6-propionate and with a, sulfate ion. Serine and arginine replacements have been made previously at, position 45 to examine the proposal that the CD3 side chain acts as a, barrier to ligand entry into the protein. Crystal structures of the, arginine-45 and serine-45 mutant metmyoglobins have been solved to 1.9 and, 2.0 A resolution, respectively. In both cases the structural changes are, confined to the site of mutation. Arginine-45 takes up a conformation, closely similar to that observed for this residue in wild-type sperm whale, myoglobin, in which it makes more extensive charge-charge and, charge-dipole interactions and appears to restrict the movement of the, distal histidine away from the ligand. The hydroxyl group of serine-45 is, disordered, but it is clear that the effect of the mutation is to open up, the solvent-exposed face of the heme pocket.
About this Structure
1MYG is a Single protein structure of sequence from Sus scrofa with SO4 and HEM as ligands. Full crystallographic information is available from OCA.
Reference
High-resolution X-ray structures of pig metmyoglobin and two CD3 mutants: Mb(Lys45----Arg) and Mb(Lys45----Ser)., Oldfield TJ, Smerdon SJ, Dauter Z, Petratos K, Wilson KS, Wilkinson AJ, Biochemistry. 1992 Sep 22;31(37):8732-9. PMID:1390659
Page seeded by OCA on Tue Nov 20 21:48:34 2007
