Ulke-Lemée Annegret, Sun David Hao, Ishida Hiroaki, Vogel Hans J, MacDonald Justin A
Department of Biochemistry & Molecular Biology, University of Calgary, Cumming School of Medicine, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.
Biochemistry Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1 N4, Canada.
BMC Biochem. 2017 Mar 21;18(1):5. doi: 10.1186/s12858-017-0080-6.
The smoothelin-like 1 protein (SMTNL1) can associate with tropomyosin (Tpm) and calmodulin (CaM), two proteins essential to the smooth muscle contractile process. SMTNL1 is phosphorylated at Ser301 by protein kinase A during calcium desensitization in smooth muscle, yet the effect of SMTNL1 phosphorylation on Tpm- and CaM-binding has yet to be investigated.
Using pull down studies with Tpm-Sepharose and CaM-Sepharose, we examined the interplay between Tpm binding, CaM binding, phosphorylation of SMTNL1 and calcium concentration. Phosphorylation greatly enhanced the ability of SMTNL1 to associate with Tpm in vitro; surface plasmon resonance yielded a 10-fold enhancement in K value with phosphorylation. The effect on CaM binding is more complex and varies with the availability of calcium.
Combining both CaM and Tpm with SMTNL1 shows that the binding to both is mutually exclusive.
类平滑肌蛋白1（SMTNL1）可与原肌球蛋白（Tpm）和钙调蛋白（CaM）结合，这两种蛋白对平滑肌收缩过程至关重要。在平滑肌钙脱敏过程中，SMTNL1在丝氨酸301位点被蛋白激酶A磷酸化，然而SMTNL1磷酸化对Tpm和CaM结合的影响尚未得到研究。
通过使用Tpm琼脂糖凝胶和CaM琼脂糖凝胶进行下拉实验，我们研究了Tpm结合、CaM结合、SMTNL1磷酸化和钙浓度之间的相互作用。磷酸化显著增强了SMTNL1在体外与Tpm结合的能力；表面等离子体共振显示，磷酸化使K值提高了10倍。对CaM结合的影响更为复杂，且随钙的可用性而变化。
将CaM和Tpm与SMTNL1结合表明，两者的结合是相互排斥的。
