A third specificity-determining site in mu 2 adaptin for sequences upstream of Yxx phi sorting motifs.
Internalization signals of the Yxx phi type (phi = bulky hydrophobic side chain) interact with the mu 2 chain of AP-2 adaptors. Internalization activity is intolerant of non-conservative substitution of either the tyrosine or the phi side chains, which bind to hydrophobic pockets in mu 2 adaptin in a conformation described as 'a two pinned plug into a socket'. P-selectin, a type I transmembrane protein, contains the Yxx phi-like sequence YGVF in its cytoplasmic domain, but substitution of either the tyrosine or phenylalanine with alanine in the full-length protein causes only small changes in the rate of endocytosis. It is shown here that the sequence YGVF contained within a peptide corresponding to the 17 COOH-terminal amino acids of P-selectin binds to mu 2 adaptin in the same fashion previously seen for other Yxx phi motifs. In addition, the P-selectin peptide binds to a third hydrophobic pocket in mu 2 adaptin through a leucine at position Y-3 in the peptide. This structure suggests that some sequences can function as a 'three pinned plug', in which internalization activity is not critically dependent on any one of the three interacting side chains.
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
D J
DJ
Owen
H
H
Setiadi
P R
PR
Evans
R P
RP
McEver
S A
SA
Green
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019007:P-Selectin / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding
D019007:P-Selectin