Dumas F, Frank S, Koebnik R, Maillet E, Lustig A, Van Gelder P
Department of Biophysical Chemistry, Biozentrum University of Basle, Klingelbergstrasse 70, Basel, CH-4056, Switzerland.
J Mol Biol. 2000 Jul 21;300(4):687-95. doi: 10.1006/jmbi.2000.3897.
Several bacterial outer membrane proteins have a periplasmic extension whose structure and function remain elusive. Here, the structure/function relationship of the N-terminal periplasmic domain of the sucrose-specific outer membrane channel ScrY was investigated. Circular dichroism and analytical centrifugation demonstrated that the N-terminal domain formed a parallel, three-stranded coiled coil. When this domain was fused to the maltose-specific channel LamB, permeation of maltooligosaccharides in liposomes increased with increasing sugar chain length whereas wild-type LamB showed the opposite effect. Current fluctuation analysis demonstrated increased off-rates for sugar transport through the fusion protein. Moreover, equilibrium dialysis showed an affinity of sucrose for the isolated N-terminal peptide. Together these results demonstrate a novel function for coiled coil domains, operating as an extended sugar slide.
