The affinity of GXXXG motifs in transmembrane helix-helix interactions is modulated by long-range communication.
Sequence motifs are responsible for ensuring the proper assembly of transmembrane (TM) helices in the lipid bilayer. To understand the mechanism by which the affinity of a common TM-TM interactive motif is controlled at the sequence level, we compared two well characterized GXXXG motif-containing homodimers, those formed by human erythrocyte protein glycophorin A (GpA, high-affinity dimer) and those formed by bacteriophage M13 major coat protein (MCP, low affinity dimer). In both constructs, the GXXXG motif is necessary for TM-TM association. Although the remaining interfacial residues (underlined) in GpA (LIXXGVXXGVXXT) differ from those in MCP (VVXXGAXXGIXXF), molecular modeling performed here indicated that GpA and MCP dimers possess the same overall fold. Thus, we could introduce GpA interfacial residues, alone and in combination, into the MCP sequence to help decrypt the determinants of dimer affinity. Using both in vivo TOXCAT assays and SDS-PAGE gel migration rates of synthetic peptides derived from TM regions of the proteins, we found that the most distal interfacial sites, 12 residues apart (and approximately 18 A in structural space), work in concert to control TM-TM affinity synergistically.
Melnyk
Roman A
RA
Division of Structural Biology and Biochemistry, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
Kim
Sanguk
S
Curran
A Rachael
AR
Engelman
Donald M
DM
Bowie
James U
JU
Deber
Charles M
CM
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002450:Cell Communication; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002942:Circular Dichroism; D004912:Erythrocytes / Q000378:metabolism; D006021:Glycophorins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D016415:Sequence Alignment
D006021:Glycophorins