The goal of the research is to elucidate the mechanism of action of the carrier molecule in a substrate-cation cotransport system in the bacterium E. coli, with specific focus on the melobiose carrier. Isolation of spontaneous mutants deficient in cation recognition and sugar recognition will be followed by analysis of their physiological abnormalities in membrane transport. The physiological effects of amino-acid substitution in the carrier molecule, particularly in membrane-spanning regions, will be examined. Use of site-directed mutagenesis is expected to provide an experimental test of the "helical hairpin" hypothesis for insertion of the melobiose carrier into membranes. Other studies will employ polyclonal antibodies in an attempt to determine the orientation of presumed "loop" regions of the carrier in the membrane. The means whereby small molecules such as sugars and inorganic ions gain entrance to cells through the lipid-rich cell membrane is a matter of fundamental interest and importance; active transport across membranes often involves specific carrier molecules and it is one of these--the melobiose carrier--that is the focus of this research. The goal of the project is to understand the molecular aspects of the carrier molecule that permit it to bind specifically to some molecules and not others, and to be inserted into cell membranes in a manner that permits cotransport of sugars and cations in appropriate directions. //

Agency
National Science Foundation (NSF)
Institute
Division of Molecular and Cellular Biosciences (MCB)
Application #
9017255
Program Officer
Robert Uffen
Project Start
Project End
Budget Start
1991-03-01
Budget End
1994-08-31
Support Year
Fiscal Year
1990
Total Cost
$210,000
Indirect Cost
Name
Harvard University
Department
Type
DUNS #
City
Cambridge
State
MA
Country
United States
Zip Code
02138