Distinct interactions between ubiquitin and the SH3 domains involved in immune signaling.
The SH3 domain is a versatile protein interaction motif that generally recognizes proline rich sequences (PRS). Recently, it has been shown that some SH3 domains in the endocytotic pathway can bind to ubiquitin. Moreover, Phe73 in the SH3 domain has been proposed to be an important determinant of the interaction, as the SH3 domains having Tyr73, either naturally or by mutation, failed to bind. Since SH3 domains are also important in immune receptor signaling, we investigated the interactions between immunologically relevant SH3 domains and ubiquitin. We observed that some of these SH3 domains can also bind to ubiquitin. Interestingly, we found that Nck2-SH3-3 bound to ubiquitin despite its Tyr at residue 73 (Tyr56 in our actual construct), but that CD2BP1-SH3 failed to bind, even though it has Phe at an equivalent position. Through detailed NMR binding studies on SH3 domains with Phes and Tyrs at the 73 position, we found that the two types of SH3 domains exhibit mechanistic differences in ubiquitin binding. We showed that the relative contribution of each binding sub-region in both SH3 domains and ubiquitin is quite different in the two binding modes. Such results raise the possibility that the mechanistic variety of these immunologically relevant SH3 domains might contribute to their functional diversity.
Kang
Jinho
J
Department of Biochemistry and BK21 Center for Advanced Medical Education, School of Medicine, Inha University, Chungsuk Building, Room 505, Shinheung-dong, Chung-gu, Incheon, 400-712, Republic of Korea.
Kang
Sunmi
S
Kwon
Hyuk Nam
HN
He
Wen
W
Park
Sunghyouk
S
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D054730:Protein Interaction Domains and Motifs / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000276:immunology; D025801:Ubiquitin / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018909:src Homology Domains / Q000235:genetics / Q000276:immunology*
D011994:Recombinant Proteins; D025801:Ubiquitin