The structure of Sky1p reveals a novel mechanism for constitutive activity.
Sky1p is the only member of the SR protein kinase (SRPK) family in Saccharomyces cerevisiae. SRPKs are constitutively active kinases that display remarkable substrate specificity and have been implicated in RNA processing. Here we present the three-dimensional structure of a fully active truncated Sky1p. Analysis of the structure and structure-based functional studies reveal that the C-terminal tail, an unusual Glu residue located in the P+1 loop, and a unique mechanism for the positioning of helix alpha C act together to render Sky1p constitutively active. We have modeled a substrate peptide bound to Sky1p. The modeled complex combined with mutagenesis studies illustrate the molecular basis for substrate recognition by this kinase and suggest a mechanism by which SRPKs catalyze a sequential phosphorylation reaction of the consecutive RS dipeptide repeats characteristic of mammalian SRPK substrates.
Nolen
B
B
Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92130, USA.
Yun
C Y
CY
Wong
C F
CF
McCammon
J A
JA
Fu
X D
XD
Ghosh
G
G
D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D005656:Fungal Proteins / Q000378:metabolism; D005804:Genes, Lethal / Q000235:genetics; D005973:Glutamine / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D055672:Static Electricity
D005656:Fungal Proteins; C077734:NPL3 protein, S cerevisiae; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D005973:Glutamine; C490216:SKY1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases