The Crystal Structure Of Saimiri Boliviensis Galectin-13 And Its Interaction With Actin

Galectin-13(Gal-13)gene is found only in primates.Gal-13 is expressed primarily in the syncytiotrophoblasts of the placenta,and can be secreted into the blood or other parts of the placenta.In humans,low levels of Gal-13 expression early in pregnancy may lead to preeclampsia.In this paper,I selected Gal-13(s Gal-13)from Saimiri boliviensis boliviensis as research target and study its structure and function,and compared it with human Gal-13(h Gal-13).Specific research contents are as follows:In this study,the plasmid of s Gal-13 was first transformed into E coli BL21(DE3),then purified the protein.The purified protein was crystallized.By analyzing the co-crystal structure of s Gal-13 combined with lactose,it was found that the difference between s Gal-13 and h Gal-13 was that,s Gal-13 exists in monomer form,while h Gal-13 exists in dimer form.The results of gel filtration proved that s Gal-13 exists in monomer form.The crystal structure also showed that s Gal-13 could bind to lactose,while h Gal-13 could not.The affinity chromatography also proved that s Gal-13 could interact with lactose.The results of erythrocyte agglutination experiment showed that s Gal-13 had the ability to agglutinate erythrocytes,and the activity of s Gal-13 was higher than that of h Gal-13,and neither lactose nor sucrose could inhibit this activity of s Gal-13.In addition,pull-down assay and biofilm interference assay were performed to determine the interaction between Gal-13 and actin.The results showed that both s Gal-13and h Gal-13 could bind actin,and lactose could not inhibit this binding,suggesting that the binding site of Gal-13 to actin was outside the sugar binding site.The results showed that the h Gal-13 mutant C136S/C138S was stronger in binding to actin than the wild-type h Gal-13,suggesting that the Gal-13 monomer was the main form of binding actin.The study also found that ATP and Ca²⁺significantly stabilized the interaction between the proteins,suggesting that Gal-13 stabilized the actin monomer soluble state(G-actin),which inhibits actin formation into a polymer state(F-actin).In summary,Gal-13 is an actin binding protein.By binding to actin,Gal-13 may inhibit the contraction of vascular smooth muscle cells,thereby reduce muscle tension.Physiologically,Gal-13 may have the effect of lowering blood pressure and relaxing the myometrium,which also explains that the mutation or reduced expression of Gal-13 gene can lead to hypertension,preeclampsia,growth restriction in utero,etc.