title: GIT1 paxillin-binding domain is a four-helix bundle, and it binds to both paxillin LD2 and LD4 motifs.
abstract: The G protein-coupled receptor kinase-interacting protein 1 (GIT1) is a multidomain protein that plays an important role in cell adhesion, motility, cytoskeletal remodeling, and membrane trafficking. GIT1 mediates the localization of the p21-activated kinase (PAK) and PAK-interactive exchange factor to focal adhesions, and its activation is regulated by the interaction between its C-terminal paxillin-binding domain (PBD) and the LD motifs of paxillin. In this study, we determined the solution structure of rat GIT1 PBD by NMR spectroscopy. The PBD folds into a four-helix bundle, which is structurally similar to the focal adhesion targeting and vinculin tail domains. Previous studies showed that GIT1 interacts with paxillin through the LD4 motif. Here, we demonstrated that in addition to the LD4 motif, the GIT1 PBD can also bind to the paxillin LD2 motif, and both LD2 and LD4 motifs competitively target the same site on the PBD surface. We also revealed that paxillin Ser(272) phosphorylation does not influence GIT1 PBD binding in vitro. These results are in agreement with the notion that phosphorylation of paxillin Ser(272) plays an essential role in regulating focal adhesion turnover.
authors.affiliation: Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
authors.forename: Ziwei M
authors.initials: ZM
authors.lastname: Zhang
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Simmerman
authors.forename: Cristina D
authors.initials: CD
authors.lastname: Guibao
authors.forename: Jie J
authors.initials: JJ
authors.lastname: Zheng
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000378:metabolism; D022001:Focal Adhesions / Q000737:chemistry / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D051419:Paxillin / Q000737:chemistry / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D054462:p21-Activated Kinases / Q000737:chemistry / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; C485648:Git1 protein, rat; D051419:Paxillin; D010750:Phosphoproteins; C496063:Pxn protein, rat; D054462:p21-Activated Kinases