Adaptable molecular interactions guide phosphorylation of the SR protein ASF/SF2 by SRPK1.
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Hagopian JC, Ma CT, Meade BR, Albuquerque CP, Ngo JC, Ghosh G, Jennings PA, Fu XD, Adams JA
Adaptable molecular interactions guide phosphorylation of the SR protein ASF/SF2 by SRPK1.
J Mol Biol. 2008 Oct 17;382(4):894-909. doi: 10.1016/j.jmb.2008.07.055. Epub 2008 Jul 26.
- PubMed ID
- 18687337 [ View in PubMed]
- 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.