Structures of Wild-Type Chloromet and L103N Hydroxomet Themiste zostericola Myohemerythrins at 1.8 Å Resolution

• Published in: Biochemistry (Easton) Vol. 36; no. 23; pp. 7044 - 7049
• Main Authors: Martins, Laura J, Hill, Christopher P, Ellis, Walther R
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 10.06.1997
• Subjects: Animals; Asparagine; Binding Sites; Crystallography, X-Ray; Hemerythrin - analogs & derivatives; Hemerythrin - chemistry; Hemerythrin - genetics; Hydrogen Bonding; Kinetics; Leucine; Ligands; Models, Molecular; Nematoda; Pigments, Biological - chemistry; Pigments, Biological - genetics; Protein Conformation; Recombinant Proteins - chemistry; Water
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi9630422

Myohemerythrin (Mhr) is a nonheme iron oxygen carrier found in the retractor muscles of marine “peanut” worms. The X-ray crystal structures of two recombinant Themiste zostericola Mhrs are reported to a resolution of 1.8 Å. Surprisingly, the met wild-type structure (R = 17.8%) was found to contain chloride bound to Fe2, while coordinated hydroxide was found in the met L103N structure (R = 18.3%). An internal water molecule was also found distal to the Fe−O−Fe center of the mutant protein, forming hydrogen bonds with the coordinated hydroxide and the OD1 atom of Asn-103. This finding is consistent with the kinetic and spectroscopic results reported for the L103N mutant Mhr [Raner, G. M., Martins, L. J., & Ellis, W. R., Jr. (1997) Biochemistry 36, 7037−7043]. Possible roles for the side chain of residue 103 (Leu in wild-type Mhr) in gating ligand binding are also discussed.