title: Adaptable molecular interactions guide phosphorylation of the SR protein ASF/SF2 by SRPK1.
abstract: The SR (arginine-serine rich) protein ASF/SF2 (also called human alternative splicing factor), an essential splicing factor, contains two functional modules consisting of tandem RNA recognition motifs (RRMs; RRM1-RRM2) and a C-terminal arginine-serine repeat region (RS domain, a domain rich in arginine-serine repeats). The SR-specific protein kinase (SRPK) 1 phosphorylates the RS domain at multiple serines using a directional (C-terminal-to-N-terminal) and processive mechanism--a process that directs the SR protein to the nucleus and influences protein-protein interactions associated with splicing function. To investigate how SRPK1 accomplishes this feat, the enzyme-substrate complex was analyzed using single-turnover and multiturnover kinetic methods. Deletion studies revealed that while recognition of the RS domain by a docking groove on SRPK1 is sufficient to initiate the processive and directional mechanism, continued processive phosphorylation in the presence of building repulsive charge relies on the fine-tuning of contacts with the RRM1-RRM2 module. An electropositive pocket in SRPK1 that stabilizes newly phosphorylated serines enhanced processive phosphorylation of later serines. These data indicate that SRPK1 uses stable, yet highly flexible protein-protein interactions to facilitate both early and late phases of the processive phosphorylation of SR proteins.
authors.affiliation: Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0636, USA.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Hagopian
authors.forename: Chen-Ting
authors.initials: CT
authors.lastname: Ma
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Meade
authors.forename: Claudio P
authors.initials: CP
authors.lastname: Albuquerque
authors.forename: Jacky Chi Ki
authors.initials: JC
authors.lastname: Ngo
authors.forename: Gourisankar
authors.initials: G
authors.lastname: Ghosh
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Jennings
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Fu
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Adams
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors
chemical_list: D009687:Nuclear Proteins; D010455:Peptides; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D000068103:Serine-Arginine Splicing Factors; C087728:SRPK1 protein, human; D017346:Protein Serine-Threonine Kinases