[1P-73] 外膜蛋白質のナノディスクへの挿入におけるBamAの役割
Bacterial outer membrane proteins (OMPs) are integral membrane protein with β-barrel structures. OMPs are inserted into the outer membrane (OM) by a β-barrel assembly machinery (BAM) complex. The BAM complex consists of five subunits (A-E), and its main component is BamA, which contains a membrane embedded β-barrel domain and five polypeptide translocation-associated (POTRA) domains. Although BamA is thought to be essential for folding and insertion of OMPs, the mechanism has not been fully elucidated. In this study, we investigated the membrane-insertion mechanism of a monomeric OMP, outer membrane protein A transmembrane domain (OmpATD), and a trimeric OMP, Haemophilus Influenzae adhesin transmembrane domain (HiaTD), using empty nanodiscs and BamA-embedded nanodiscs. Assembly of HiaTD into the empty nanodiscs was hardly observed. In contrast, HiaTD was assembled into the BamA-embedded nanodiscs. The insertion of OmpATD into the nanodiscs was observed both in the presence and absence of BamA, and its rate was accelerated by BamA. These results indicate that BamA facilitates OMPs insertion into nanodiscs.