Tpr1, a Schizosaccharomyces pombe protein involved in potassium transport

The Schizosaccharomyces pombe Tpr1 was isolated as suppressor of the Saccha romyces cerevisiae Delta trk1,2 potassium uptake deficient phenotype, Tpr1, for tetratrico peptide repeat, encodes a 1039 amino acid residues protein with several reiterated TPR units displaying significant homology to p150(T SP),a recently identified phosphoprotein of mouse, to S, cerevisiae CTR9 an d to related sequences of human, Caenorhabditis elegans, Methanoccocus jann aschii and Al Arabidopsis thaliana. Expression of Tpr1 restored growth on 0 .2 mM K+ media, induced K+ transport with a K-T Of 4.6 mM and resumed inwar d currents of -90 p Angstrom at -250 mV (pH 7.2) conducting K+ and other al kali-metal ions. The tetratrico peptide repeat is a degenerate motif of 34 amino acids that is repeated several times within TPR-containing proteins a nd has been suggested to mediate protein-protein interactions. The sequence and putative binding properties of Tpr1 suggest the protein unlikely as tr ansporter but involved in the enhancement of K+ uptake via conventional car riers. (C) 1999 Federation of European Biochemical Societies.