PDBsum entry 1mym

Oxygen transport

PDB id: 1mym

Contents

Protein chain

154 a.a.

Ligands

SO4

HEM-CMO

Waters ×147

References listed in PDB file

Key reference

• Title: Structural determinants of the stretching frequency of co bound to myoglobin.
• Authors: T.Li, M.L.Quillin, G.N.Phillips, J.S.Olson.
• Ref.: Biochemistry, 1994, 33, 1433-1446. [DOI no: 10.1021/bi00172a021]
• PubMed id: 8312263

Abstract

In order to assess the relative importance of polar versus steric interactions, infrared spectra and overall CO binding properties were measured at room temperature for 41 different recombinant myoglobins containing mutations at His64(E7), Val68(E11), Phe43(CD1), Arg45(CD3), Phe46(CD4), and Leu29(B10). The results were compared to the crystal structures of wild-type, Phe29, Val46, Ala68, Phe68, Gln64, Leu64, and Gly64 sperm whale CO-myoglobin and that of Thr68 pig CO-myoglobin. As observed in several previous studies, replacement of the distal histidine (His64) with aliphatic amino acids results in the appearance of a single IR band in the 1960-1970-cm-1 region and in large increases in CO affinity (KCO). More complex behavior is observed for Gly, Ala, Gln, Met, and Trp substitutions at position 64, but in each case there is a net increase in the intensity of this high-frequency component. Replacement of Val68 with Ala, Leu, Ile, and Phe produces little effect on the IR spectrum, whereas these mutations cause 20-fold changes in KCO, presumably due to steric effects. Replacement of Val68 with Thr decreases KCO 4-5-fold, whereas the position of the major IR band increases from 1945 to 1961 cm-1. Replacement of Val68 with Asn also causes a large decrease in KCO, but in this case, the peak position of the major IR band decreases from 1945 to 1916 cm-1. Nine replacements were made in the CD corner at positions 43, 45, and 46. All of the resultant mutants show increased stretching frequencies that can be correlated with movement of the imidazole side chain of His64 away from the bound ligand. All five substitutions at position 29 cause changes in the IR spectra. The Leu29-->Phe mutation had the largest effect, producing a single band centered at 1932 cm-1. Together these data demonstrate that there is little direct correlation between affinity, vCO, and Fe-C-O geometry. The major factor governing vCO appears to be the electrostatic potential surrounding the bound ligand and not steric hindrance. The presence of positive charges from proton donors, such as N epsilon of His64 and N delta of Asn68, cause a decrease in the bond order and stretching frequency of bound CO. In contrast, the negative portion of the Thr68 dipole points directly toward the bound ligand and increases the C-O bond order and stretching frequency. Movement of His64 away from the bound ligand or replacement of this residue with aliphatic amino acids prevents hydrogen-bonding interactions, causing vCO to increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Secondary reference #1

• Title: High-Resolution crystal structures of distal histidine mutants of sperm whale myoglobin.
• Authors: M.L.Quillin, R.M.Arduini, J.S.Olson, G.N.Phillips.
• Ref.: J Mol Biol, 1993, 234, 140-155.
• PubMed id: 8230194

Note: In the PDB file this reference is annotated as "TO BE PUBLISHED". The citation details given above have been manually determined.

Secondary reference #2

• Title: Crystal structure of myoglobin from a synthetic gene.
• Authors: G.N.Phillips, R.M.Arduini, B.A.Springer, S.G.Sligar.
• Ref.: Proteins, 1990, 7, 358-365.
• PubMed id: 2199973

Secondary reference #3

• Title: High-Level expression of sperm whale myoglobin in escherichia coli.
• Authors: B.A.Springer, S.G.Sligar.
• Ref.: Proc Natl Acad Sci U S A, 1987, 84, 8961-8965. [DOI no: 10.1073/pnas.84.24.8961]
• PubMed id: 3321062