Fig. 2.

Models of holoBirA-BCCP87 heterodimer (A) and holoBirA homodimer (B). Rotation of the molecules by 90° displays cross-sections of the heterodimer interface (bottom left) and homodimer interface (bottom right), highlighting the surface loops involved in the two interactions. All models were created using Pymol³⁹ with input file 2EWN for the homodimer and a file constructed by Zachary Wood for the heterodimer. This model, which uses the experimentally determined structure of the Pyroccocushorikoshi biotin protein ligase:BCCP complex as a template (2EJG)¹⁹, was constructed using the holoBirA monomer coordinates from 2EWN¹² and the coordinates for apoBCCP87 (1BDO)⁴⁰ C. Multiple sequence alignment of several bifunctional microbial biotin protein ligases performed using Clustal W.¹⁶ The color codes for loop sequences correspond to the coloring of loops in the models in A and B.