The C-terminal tetrapeptide HWFW of the Chlorella HUP1 hexose/H+-symporteris essential for full activity and an alpha-helical structure of the C-terminus

C-terminal tails of plant hexose/H+-symporters of the major facilitator sup erfamily contain a highly conserved motif of four amino acids: HWFW. A dele tion of these four amino acids in the Chlorella HUP1 protein leads to a dec rease in transport activity by a factor of 3-4. The mutated tail is highly sensitive to trypsin; it does not show alpha-helical conformation in contra st to the wild type C-terminal peptide with an alpha-helical content of at least 15%, The production of monoclonal antibody 416B8 recognizing an epito pe within the central loop of HUP1 protein has been a prerequisite for the experiments described. (C) 2000 Federation of European Biochemical Societie s.