SR protein kinase 1 is resilient to inactivation.
SR protein kinase 1 (SRPK1) is a constitutively active kinase, which processively phosphorylates multiple serines within its substrates, ASF/SF2. We describe crystallographic, molecular dynamics, and biochemical results that shed light on how SRPK1 preserves its constitutive active conformation. Our structure reveals that unlike other known active kinase structures, the activation loop remains in an active state without any specific intraprotein interactions. Moreover, SRPK1 remains active despite extensive mutation to the activation segment. Molecular dynamics simulations reveal that SRPK1 partially absorbs the effect of mutations by forming compensatory interactions that maintain a catalytically competent chemical environment. Furthermore, SRPK1 is similarly resistant to deletion of its spacer loop region. Based upon a model of SRPK1 bound to a segment encompassing the docking motif and active-site peptide of ASF/SF2, we suggest a mechanism for processive phosphorylation and propose that the atypical resiliency we observed is critical for SRPK1's processive activity.
Ngo
Jacky Chi Ki
JC
Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
Gullingsrud
Justin
J
Giang
Kayla
K
Yeh
Melinda Jean
MJ
Fu
Xiang-Dong
XD
Adams
Joseph A
JA
McCammon
J Andrew
JA
Ghosh
Gourisankar
G
D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D000068103:Serine-Arginine Splicing Factors
D009687:Nuclear Proteins; D010455:Peptides; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D000068103:Serine-Arginine Splicing Factors; C490216:SKY1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases