The GxxxG motif: A framework for transmembrane helix-helix association

• Published in: Journal of molecular biology 2000-02, Vol.296 (3), p.911-919
• Main Authors: Russ, William P, Engelman, Donald M
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs - genetics; Amino Acid Sequence; Amino Acid Substitution - genetics; association; Bacterial Proteins - genetics; Bacterial Proteins - physiology; Binding Sites; Chloramphenicol Resistance; Cloning, Molecular; Consensus Sequence - genetics; Databases, Factual; Dimerization; DNA-Binding Proteins - genetics; DNA-Binding Proteins - physiology; Escherichia coli - cytology; Escherichia coli - genetics; Escherichia coli - physiology; glycine; Glycophorin - chemistry; Glycophorin - genetics; Glycophorin - metabolism; Intracellular Membranes - metabolism; membrane protein; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Models, Molecular; Peptide Library; protein folding; Protein Structure, Secondary; Protein Structure, Tertiary; Thermodynamics; TOXCAT; Transcription Factors - genetics; Transcription Factors - physiology
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1006/jmbi.1999.3489

In order to identify strong transmembrane helix packing motifs, we have selected transmembrane domains exhibiting high-affinity homo-oligomerization from a randomized sequence library based on the right-handed dimerization motif of glycophorin A. Sequences were isolated using the TOXCAT system, which measures transmembrane helix-helix association in the Escherichia coli inner membrane. Strong selection was applied to a large range of sequences (∼10 7 possibilities) and resulted in the identification of sequence patterns that mediate high-affinity helix-helix association. The most frequent motif isolated, GxxxG, occurs in over 80 % of the isolates. Additional correlations suggest that flanking residues act in concert with the GxxxG motif, and that size complementarity is maintained at the interface, consistent with the idea that the identified sequence patterns represent packing motifs. The convergent identification of similar sequence patterns from an analysis of the transmembrane domains in the SwissProt sequence database suggests that these packing motifs are frequently utilized in naturally occurring helical membrane proteins.