1xkj
From Proteopedia
BACTERIAL LUCIFERASE BETA2 HOMODIMER
Overview
The crystal structure of the beta 2 homodimer of Vibrio harveyi luciferase has been determined to 2.5 A resolution by molecular replacement. Crystals were grown serendipitously using the alpha beta form of the enzyme. The subunits of the homodimer share considerable structural homology to the beta subunit of the alpha beta luciferase heterodimer. The four C-terminal residues that are disordered in the alpha beta structure are fully resolved in our structure. Four peptide bonds have been flipped relative to their orientations in the beta subunit of the alpha beta structure. The dimer interface of the homodimer is smaller than the interface of the heterodimer in terms of buried surface area and number of hydrogen bonds and salt links. Inspection of the subunits of our structure suggests that FMNH2 cannot bind to the beta 2 enzyme at the site that has been proposed for the alpha beta enzyme. However, we do uncover a potential FMNH2 binding pocket in the dimer interface, and we model FMN into this site. This proposed flavin binding motif is consistent with several lines of biochemical and structural evidence and leads to several conclusions. First, only one FMNH2 binds per homodimer. Second, we predict that reduced FAD and riboflavin should be poor substrates for beta 2. Third, the reduced activity of beta 2 compared to alpha beta is due to solvent exposure of the isoalloxazine ring in the beta 2 active site. Finally, we raise the question of whether our proposed flavin binding site could also be the binding site for flavin in the alpha beta enzyme.
About this Structure
1XKJ is a Single protein structure of sequence from Vibrio harveyi. Full crystallographic information is available from OCA.
Reference
Structure of bacterial luciferase beta 2 homodimer: implications for flavin binding., Tanner JJ, Miller MD, Wilson KS, Tu SC, Krause KL, Biochemistry. 1997 Jan 28;36(4):665-72. PMID:9020763 Page seeded by OCA on Sat May 3 15:08:46 2008
