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. Author manuscript; available in PMC: 2012 Aug 16.
Published in final edited form as: Biochemistry. 2011 Jul 15;50(32):6888–6900. doi: 10.1021/bi2007993

Figure 1. Structure and Phosphorylation Mechanism of SRSF1.

Figure 1

A) SRSF1 Domain Structure. SRSF1 has two RRMs and a C-terminal RS domain composed of RS1 and RS2 segments. B) Structure of SRPK1 core with AMPPNP and the N-terminal portion of RS1 segment (R204SRSRSR) bound to the docking groove in the large lobe. Arginines are colored blue and serines are colored red. A hydrogen bond is formed between the hydroxyl of Ser207 and the backbone carbonyl of Ser209. RRM2 is not displayed in this depiction. C) Phosphorylation Model. SRPK1 binds SRSF1 with high affinity using an electronegative docking groove that initially recognizes the N-terminal portion of RS1. Upon progressive phosphorylation, RS1 is threaded through the docking groove and into the active site in a C-to-N-terminal direction. In later phosphorylation stages, β4 from RRM2 unfolds and binds in the docking groove and phosphoserines in RS1 are stabilized by an electropositive site (P+2 site)