Structurally unique yeast and mammalian serine-arginine protein kinases catalyze evolutionarily conserved phosphorylation reactions.
The mammalian serine-arginine (SR) protein, ASF/SF2, contains multiple contiguous RS dipeptides at the C terminus, and approximately 12 of these serines are processively phosphorylated by the SR protein kinase 1 (SRPK1). We have recently shown that a docking motif in ASF/SF2 specifically interacts with a groove in SRPK1, and this interaction is necessary for processive phosphorylation. We previously showed that SRPK1 and its yeast ortholog Sky1p maintain their active conformations using diverse structural strategies. Here we tested if the mechanism of ASF/SF2 phosphorylation by SRPK is evolutionarily conserved. We show that Sky1p forms a stable complex with its heterologous mammalian substrate ASF/SF2 and processively phosphorylates the same sites as SRPK1. We further show that Sky1p utilizes the same docking groove to bind yeast SR-like protein Gbp2p and phosphorylates all three serines present in a contiguous RS dipeptide stretch. However, the mechanism of Gbp2p phosphorylation appears to be non-processive. Thus, there are physical attributes of SR and SR-like substrates that dictate the mechanism of phosphorylation, whereas the ability to processively phosphorylate substrates is inherent to SR protein kinases.
Lukasiewicz
Randall
R
Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, California 92093-0375, USA.
Velazquez-Dones
Adolfo
A
Huynh
Nhat
N
Hagopian
Jonathan
J
Fu
Xiang-Dong
XD
Adams
Joseph
J
Ghosh
Gourisankar
G
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D019143:Evolution, Molecular; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry; D016601:RNA-Binding Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D000068103:Serine-Arginine Splicing Factors
C474034:Gbp2 protein, S cerevisiae; D009687:Nuclear Proteins; D010455:Peptides; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D000068103:Serine-Arginine Splicing Factors; D011494:Protein Kinases; C490216:SKY1 protein, S cerevisiae; C087728:SRPK1 protein, human; D017346:Protein Serine-Threonine Kinases