Crystal structure of obelin after Ca2+-triggered bioluminescence suggests neutral coelenteramide as the primary excited state.

ABSTRACT: The crystal structure at 1.93-A resolution is determined for the Ca2+-discharged obelin containing three bound calcium ions as well as the product of the bioluminescence reaction, coelenteramide. This finding extends the series of available spatial structures of the ligand-dependent conformations of the protein to four, the obelin itself, and those after the bioluminescence reaction with or without bound Ca2+ and/or coelenteramide. Among these structures, global conformational changes are small, typical of the class of "calcium signal modulators" within the EF-hand protein superfamily. Nevertheless, in the active site there are significant repositions of two residues. The His-175 imidazole ring flips becoming almost perpendicular to the original orientation corroborating the crucial import

SUBMITTER: Liu ZJ 

PROVIDER: S-EPMC1413834 | biostudies-literature | 2006 Feb

REPOSITORIES: biostudies-literature