title: Cloning and expression of a hepatic microsomal glucose transport protein. Comparison with liver plasma-membrane glucose-transport protein GLUT 2.
abstract: Antibodies raised against a 52 kDa rat liver microsomal glucose-transport protein were used to screen a rat liver cDNA library. Six positive clones were isolated. Two clones were found to be identical with the liver plasma-membrane glucose-transport protein termed GLUT 2. The sequence of the four remaining clones indicates that they encode a unique microsomal facilitative glucose-transport protein which we have termed GLUT 7. Sequence analysis revealed that the largest GLUT 7 clone was 2161 bp in length and encodes a protein of 528 amino acids. The deduced amino acid sequence of GLUT 7 shows 68% identity with the deduced amino acid sequence of rat liver GLUT 2. The GLUT 7 sequence is six amino acids longer than rat liver GLUT 2, and the extra six amino acids at the C-terminal end contain a consensus motif for retention of membrane-spanning proteins in the endoplasmic reticulum. When the largest GLUT 7 clone was transfected into COS 7 cells the expressed protein was found in the endoplasmic reticulum and nuclear membrane, but not in the plasma membrane. Microsomes isolated from the transfected COS 7 cells demonstrated an increase in their microsomal glucose-transport capacity, demonstrating that the GLUT 7 clone encodes a functional endoplasmic-reticulum glucose-transport protein.
authors.affiliation: Department of Child Health, Ninewells Hospital and Medical School, Dundee, Scotland, U.K.
authors.forename: I D
authors.initials: ID
authors.lastname: Waddell
authors.forename: A G
authors.initials: AG
authors.lastname: Zomerschoe
authors.forename: M W
authors.initials: MW
authors.lastname: Voice
authors.forename: A
authors.initials: A
authors.lastname: Burchell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D015870:Gene Expression; D015723:Gene Library; D007150:Immunohistochemistry; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection
chemical_list: D009004:Monosaccharide Transport Proteins