Porin and porin-associated protein (PAP) of Rhodospirillum rubrum FR1

Uwe Neumann; Roland Benz; Jurg P. Rosenbusch; Bernd Stahl; Jurgen Weckesser

doi:10.1099/13500872-141-12-3155

Volume 141, Issue 12

Research Article

Free

Porin and porin-associated protein (PAP) of Rhodospirillum rubrum FR1

Uwe Neumann¹, Roland Benz², Jurg P. Rosenbusch³, Bernd Stahl⁴ and Jurgen Weckesser¹
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Affiliations: ¹ Institut für Biologie II, Mikrobiologie, Schánzlestraβe 1, D-79104 Freiburg i. Br., Germany ² Lehrstuhl für Biotechnologie, Biozentrum der Universitat Würzburg, Am Hubland, D-97074 Wüzburg, Germany ³ Biozentrum der Universitat Basal, Abteilung Mikrobiologie Klingelbergstrasse 70, CH-4056 Basel, Switzerland ⁴ Institut für Medizinische Physik und Biophysik der Universitat Münster, Robert-Koch-Straβe 31, D-48149 Münster,Germany
Tel: +49 761 203 2638. Fax: +49 761 203 2647.
Published: 01 December 1995 https://doi.org/10.1099/13500872-141-12-3155

Abstract

The porin of Rhodospirillum rubrum FR1 was found in the outer membrane as a complex with a relatively small (32 kDa) porin-associated protein (PAP). The porin moiety of the complex consisted of a trimer which revealed a mainly β-sheet structure, while the porin-PAP complex also contained a significant α-helical portion. Isolated PAP exhibited a mostly α-helical structure. The porin-PAP complex had the same single-channel conductivity (2.8 nS) as the isolated porin, demonstrating that PAP did not affect the porin channel size. Differential extraction of the cell wall fraction with N,N-dimethyldodecylamine N-oxide revealed that PAP stabilized the porin in the outer membrane. EDTA caused dissociation of the porin-PAP complex, indicating that divalent cations were involved in formation of this complex.

Received: 19/05/1995