Investigation of the Potra Domains from Cyanobacterial Omp85 by Peldor Spectroscopy

Abstract

Omp85 proteins contain a C-terminal transmembrane beta-barrel and a soluble N terminus with a varying number of polypeptide-transport-associated (POTRA) domains.1 N-terminal POTRA domains (P1 and P2) of Omp85 from the cyanobacterium Anabaena sp. PCC 7120 might have functions in substrate recognition and heterooligomerization.2 P3 is implied in regulation of protein transport by its L1-loop. Molecular dynamics (MD) simulations predicted that P2 and P3 are fixed in orientation, consistent with a short connection and a large interface between both domains, and that there is a hinge between P1 and P2.2 In this study we used site-directed spin labeling (SDSL) to investigate the conformational flexibility between POTRA domains by PELDOR (pulsed electron-electron double resonance) spectroscopy.3-5 The experimental results will be compared with the MD calculations and X-ray structures.2 Further studies of the interaction of POTRA domains with chaperones and substrates are underway.