Novel inter- and intrasubunit contacts between transport-relevant residues of the homodimeric mitochondrial phosphate transport protein

• Published in: Biochemical and biophysical research communications Vol. 320; no. 3; pp. 685 - 688
• Main Author: Wohlrab, Hartmut
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.07.2004
• Subjects: Amino Acid Sequence; Binding Sites; Computer Simulation; Coupled transport; Dimerization; Mitochondria; Mitochondrial Proteins - analysis; Mitochondrial Proteins - chemistry; Models, Molecular; Molecular Sequence Data; Phosphate; Phosphate Transport Proteins - analysis; Phosphate Transport Proteins - chemistry; Protein Binding; Protein Conformation; Protein Structure, Tertiary; Protein Transport; Sequence Analysis, Protein; Sequence Homology, Amino Acid; Serine - chemistry; Structure-Activity Relationship; Transport protein; Mitochondria; Coupled transport; Transport protein; Phosphate
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2004.05.211

Ser158 is located near the middle of the matrix loop connecting transmembrane helices C and D of the mitochondrial phosphate transport protein (PTP). The mutant Ser158Thr PTP is transport-inactive. His32 is located near the middle of transmembrane helix A and Thr79 is located 5 residues away from transmembrane helix B and its N-terminal (matrix end). Single site mutant PTPs that have either residue replaced with Ala are transport-inactive. Based on the high resolution structure of a subunit of the bovine ADP/ATP translocase, on sequence similarities between members of the mitochondrial transport protein family, and on the PTP subunit/subunit contact site between transmembrane A helices, it is now suggested that the Ser158 site is at the PTP subunit/subunit contact site. This contact site is essential for keeping the transport cycles catalyzed by the two PTP subunits 180° out of phase. The data also suggest that His32 and Thr79 of the same subunit interact and couple the phosphate and the proton transport paths.