Structural Analysis of Marine Flavobacterium Protein Glutaminase Reveals a "Gatekeeper" Residue Affecting Its...

A novel protein glutaminase (PG) named FBPG, derived from Flavobacterium sp. 316, was the focus of analysis for the relationship between its structure and function. Through successful heterologous expression in E. coli BL21 (DE3), a mature peptide (mFBPG) was purified following trypsin digestion, demonstrating a specific activity of 1.43 U/mg and a mass of 20.13 kDa. The elucidation of its crystal structure via X-ray diffraction unveiled a composition comprising seven α-helices and 14 β-sheets. Molecular docking studies identified residue R225 as a pivotal "gatekeeper" regulating substrate entry into the catalytic site. Furthermore, the specific activity of the modified variant was 10.38 U/mg after substituting R225 with lysine (R225K), a remarkable 6.37-fold enhancement over that of wild-type mFBPG. These observations enhance our comprehension of the PG enzyme family and lay the foundation for improving their performance.