The medium subunits of adaptor complexes recognize distinct but overlapping sets of tyrosine-based sorting signals.
Tyrosine-based sorting signals conforming to the motif YXXO (Y is tyrosine, X is any amino acid, and O is an amino acid with a bulky hydrophobic side chain (leucine, isoleucine, phenylalanine, methionine, valine)) interact with the medium (mu) subunits of clathrin adaptor (AP) complexes. We have analyzed the selectivity of interaction between YXXO signals and the mu1, mu2, and mu3 (A or B) subunits of the AP-1, AP-2, and AP-3 complexes, respectively, by screening a combinatorial XXXYXXO library using the yeast two-hybrid system. All the medium subunits were found to prefer proline at position Y+2, suggesting that YXXO signals are stabilized by a bend in the polypeptide backbone. Other than for this common preference, each medium subunit favored specific sets of residues at the X and O positions; these preferences were consistent with the proposed roles of the different adaptor complexes in rapid endocytosis and lysosomal targeting. A considerable specificity overlap was also revealed by these analyses, suggesting that additional factors, such as the context of the signals, must be important determinants of recognition.
Ohno
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H
The, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
Aguilar
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RC
Yeh
D
D
Taura
D
D
Saito
T
T
Bonifacino
J S
JS
D033961:Adaptor Protein Complex 1; D033962:Adaptor Protein Complex 2; D033963:Adaptor Protein Complex 3; D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000378:metabolism*; D015723:Gene Library; D008247:Lysosomes / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D034041:Monomeric Clathrin Assembly Proteins; D009419:Nerve Tissue Proteins / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry; D021382:Protein Sorting Signals / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry*; D014714:Vertebrates
D033961:Adaptor Protein Complex 1; D033962:Adaptor Protein Complex 2; D033963:Adaptor Protein Complex 3; D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; D008565:Membrane Proteins; D034041:Monomeric Clathrin Assembly Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D021382:Protein Sorting Signals; C499066:adaptor protein complex 1, mu 1 subunit; C499065:adaptor protein complex 1, mu 2 subunit; C438885:adaptor protein complex 2, mu 1 subunit; C438886:adaptor protein complex 2, mu 2 subunit; C439023:clathrin assembly protein AP180; D014443:Tyrosine