supported by the National Natural Science Foundation of China (Grant Nos 20773006 and 30670497);the Beijing Natural Science Foun-dation (Grant Nos 7082006 and 5072002);the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No 200800050003)
Based on the crystal structure of the vitamin B12 transporter protein of Escherichia coli(BtuCD) a system consisting of the BtuCD transmembrane domain(BtuC) and the palmitoyloleoyl phosphatidylcholine(POPC) lipid bila...