Rt. Yan et Pc. Maloney, RESIDUES IN THE PATHWAY THROUGH A MEMBRANE TRANSPORTER, Proceedings of the National Academy of Sciences of the United Statesof America, 92(13), 1995, pp. 5973-5976
The structure of solute transporters is understood largely from analys
is of their amino acid sequences, and more direct information is great
ly needed. Here we report work that applies cysteine scanning mutagene
sis to describe structure-function relations in UhpT, a bacterial memb
rane transporter. By using an impermeant SH-reactive agent to probe si
ngle-cysteine variants, we show that UhpT transmembrane segment 7 span
s the membrane as an alpha-helix and that the central portion of this
helix is exposed to both membrane surfaces, forming part of the transl
ocation pathway through this transporter.