Structures of wild-type chloromet and L103N hydroxomet Themiste zostericola myohemerythrins at 1.8 A resolution.
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 A. 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.
Martins
L J
LJ
Department of Chemistry, University of Utah, Salt Lake City 84112, USA.
Hill
C P
CP
Ellis
W R
WR
D000818:Animals; D001216:Asparagine; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006422:Hemerythrin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics; D006860:Hydrogen Bonding; D007700:Kinetics; D007930:Leucine; D008024:Ligands; D008958:Models, Molecular; D009348:Nematoda; D010860:Pigments, Biological / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D014867:Water
D006422:Hemerythrin; D008024:Ligands; D010860:Pigments, Biological; D011994:Recombinant Proteins; C008571:myohemerythrin; D014867:Water; D001216:Asparagine; D007930:Leucine