Gaf-1, a gamma -SNAP-binding protein associated with the mitochondria.
The role of alpha/beta-SNAP (Soluble NSF Attachment Protein) in vesicular trafficking is well established; however, the function of the ubiquitously expressed gamma-SNAP remains unclear. To further characterize the cellular role of this enigmatic protein, a two-hybrid screen was used to identify new, gamma-SNAP-binding proteins and to uncover potentially novel functions for gamma-SNAP. One such SNAP-binding protein, termed Gaf-1 (gamma-SNAP associate factor-1) specifically binds gamma- but not alpha-SNAP. The full-length Gaf-1 (75 kDa) is ubiquitously expressed and is found stoichiometrically associated with gamma-SNAP in cellular extracts. This binding is distinct from other SNAP interactions since no alpha-SNAP or NSF coprecipitated with Gaf-1. Subcellular fractionation and immunofluorescence analysis show that Gaf-1 is peripherally associated with the outer mitochondrial membrane. Only a fraction of gamma-SNAP was mitochondrial with the balance being either cytosolic or associated with other membrane fractions. GFP-gamma-SNAP and the C-terminal domain of Gaf-1 both show a reticular distribution in HEK-293 cells. This reticular structure colocalizes with Gaf-1 and mitochondria as well as with microtubules but not with other cytoskeletal elements. These data identify a class of gamma-SNAP interactions that is distinct from other members of the SNAP family and point to a potential role for gamma-SNAP in mitochondrial dynamics.
Chen
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Department of Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA.
Xu
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He
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Medrano
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Whiteheart
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D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D013379:Substrate Specificity; D014162:Transfection; D014404:Tubulin / Q000378:metabolism; D033921:Vesicular Transport Proteins
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; C485422:RAB11FIP5 protein, human; D011994:Recombinant Proteins; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D014404:Tubulin; D033921:Vesicular Transport Proteins