Intramolecular interactions regulate SAP97 binding to GKAP.
Membrane-associated guanylate kinase homologs (MAGUKs) are multidomain proteins found to be central organizers of cellular junctions. In this study, we examined the molecular mechanisms that regulate the interaction of the MAGUK SAP97 with its GUK domain binding partner GKAP (GUK-associated protein). The GKAP-GUK interaction is regulated by a series of intramolecular interactions. Specifically, the association of the Src homology 3 (SH3) domain and sequences situated between the SH3 and GUK domains with the GUK domain was found to interfere with GKAP binding. In contrast, N-terminal sequences that precede the first PDZ domain in SAP97, facilitated GKAP binding via its association with the SH3 domain. Utilizing crystal structure data available for PDZ, SH3 and GUK domains, molecular models of SAP97 were generated. These models revealed that SAP97 can exist in a compact U-shaped conformation in which the N-terminal domain folds back and interacts with the SH3 and GUK domains. These models support the biochemical data and provide new insights into how intramolecular interactions may regulate the association of SAP97 with its binding partners.
Wu
H
H
University of Alabama at Birmingham, Department of Neurobiology, 1719 Sixth Avenue South CIRC 589, Birmingham, AL 35294-0021, USA.
Reissner
C
C
Kuhlendahl
S
S
Coblentz
B
B
Reuver
S
S
Kindler
S
S
Gundelfinger
E D
ED
Garner
C C
CC
D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites; D018938:Caco-2 Cells; D000074288:Discs Large Homolog 1 Protein; D051528:Guanylate Kinases; D006801:Humans; D007365:Intercellular Junctions / Q000378:metabolism; D046911:Macromolecular Substances; D008565:Membrane Proteins; D008958:Models, Molecular; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009703:Nucleoside-Phosphate Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000074407:SAP90-PSD95 Associated Proteins; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; C000614187:DLGAP1 protein, human; D000074288:Discs Large Homolog 1 Protein; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; D000074407:SAP90-PSD95 Associated Proteins; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases