title: The GxxxG motif: a framework for transmembrane helix-helix association.
abstract: 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 ( approximately 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.
authors.affiliation: Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT, 06520-8114, USA.
authors.forename: W P
authors.initials: WP
authors.lastname: Russ
authors.forename: D M
authors.initials: DM
authors.lastname: Engelman
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D001665:Binding Sites; D002702:Chloramphenicol Resistance; D003001:Cloning, Molecular; D016384:Consensus Sequence / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D016208:Databases, Factual; D019281:Dimerization; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000502:physiology; D006021:Glycophorins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D019151:Peptide Library; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D006021:Glycophorins; D008565:Membrane Proteins; D019151:Peptide Library; D014157:Transcription Factors; C066719:toxR protein, bacteria