Putative interhelical interactions within the PheP protein revealed by second-site suppressor analysis.
Highly conserved glycine residues within span I and span II of the phenylalanine and tyrosine transporter PheP were shown to be important for the function of the wild-type protein. Replacement by amino acids with increasing side chain volume led to progressive loss of transport activity. Second-site suppression studies performed with a number of the primary mutants revealed a tight packing arrangement between spans I and II that is important for function and an additional interaction between spans I and III. We also postulate that a third motif, GXXIG, present in span I and highly conserved within different members of the amino acid-polyamine-organocation family, may function as a dimerization motif. Surprisingly, other highly conserved residues, such as Y60 and L41, could be replaced by various residues with no apparent loss of activity.
Dogovski
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Department of Microbiology and Immunology, The University of Melbourne, Victoria 3010, Australia.
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Pittard
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D000595:Amino Acid Sequence; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005998:Glycine / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009690:Nucleic Acid Conformation; D015398:Signal Transduction
D026921:Amino Acid Transport Systems, Neutral; D001426:Bacterial Proteins; C069320:phenylalanine-specific permease, E coli; D005998:Glycine