作者: T. Caspari , R. Stadler , N. Sauer , W. Tanner
DOI: 10.1016/S0021-9258(17)41890-4
关键词: Transmembrane domain 、 Biochemistry 、 Arginine 、 Glucose transporter 、 Biology 、 Peptide sequence 、 Amino acid 、 Glutamine 、 Symporter 、 Protein structure
摘要: The Clorella kessleri HUP 1 gene coding for a hexose/H+ symporter has been expressed in glucose uptake-deficient mutant of Schizosaccharomyces pombe. transformants are able to grow on and accumulate 3-O-methylglucose 100-fold. This system used test the activity specifically mutated cDNAs. All three histidyl residues were exchanged with arginine (H73R, H170R, H495R) without major effect transport activity. When Asp-44 within first transmembrane helix was replaced by Asn, transporter inactive; replacement Glu (D44E) resulted loss 90% 15-fold increased Km value. Glutamine conserved all transporters sequenced so far exchanged: Q179N (in 5), Q298G Q299N (both 7). Whereas only small change, both showed an increase factor 10. Inserting 4 additional amino acids each into two largest loops (1 6) reduced dramatically; latter case this due decreased protein synthesis or stability. Two COOH-terminal deletions (-27 -43 acids) also tested. 27 acids, but not 43 could be removed affecting