Structure and function of the Na+/glucose cotransporter.

摘要: Cotransporters are a major class of membrane transport proteins that responsible for the accumulation nutrients, neurotransmitters, osmolytes and ions in cells from bacteria to man. The energy solute comes proton and/or sodium electrochemical gradients exist across cell membranes. A problem biology is how coupled these potential gradients. primary example this intestinal brush border Na+/glucose cotransporter (SGLT1), first described by Bob Crane 1960. Over 35 members SGLT1 gene family have been identified animal cells, yeast bacteria, all share common core structure 13 transmembrane (TM) helices. Electrophysiological techniques used examine function several members, chimeras mutants expressed heterologous systems such as Xenopus laevis oocytes. These revealed cotransporters multi-functional proteins: they 1). uncoupled passive Na+ (Na+ uniport); 2). down-hill water absence substrate; 3). Na+/substrate cotransport; 4). Na+/substrate/water cotransport. sugar binding translocation pathway formed 4 TM helices near C-terminal protein, 10-13. We propose N-terminal domains translocation, cotransport results interactions between N- protein.