The Preparation Of A Novel Low Density Lipoprotein Absobent

Numerous studies have demonstrated that the increased level of low density lipoprotein (LDL) in the blood is an independent risk factor of atherosclerotic diseases. In order to study the physical-chemical properties and functions of LDL researchers have invented a variety of LDL separation methods, such as ultracentrifugation, chemical precipitation, gel filtration and affinity chromatography. However, each of them has its disadvantages. In addition, LDL removal is often used to decrease LDL cholesterol levels of blood in some clinical practice. However, the currently employed LDL aphaeresis systems not only remove LDL but also absorb other "good" proteins from blood.Previously research reported that the streptococcal collagen-like protein 1 (Scll) of M41-type group A streptococcus (GAS) could specifically bind to LDL. In the present study, a novel LDL absorbent was prepared based on these findings.Scll was cloned into pASK-IBA2 from M41-type GAS, and expressed in E. coli. Then V region of Scll was equally separated into two parts, V1 and V2 region, and linked with CL-L region respectively, designated as ScllL and ScllT. The genes were cloned into pASK-IBA2 and expressed in E. coli as well. The interactions of recombinant proteins with plasma lipoproteins were detected with affinity chromatography binding assays. The results indicated that both rScll and rScllT could specifically bind LDL, but rScllL could not, which implied the V2 region of Scll was responsible for its binding to LDL. In addition, HDL could bind to rScll but not to rScllT. In order to prepare LDL absorbent purified rScll and rScllT were coupled to NHS-activated sepharose, respectively. The rScll-sepharose could specifically adsorb LDL and HDL in plasma. but rScllT-sepharose only adsorbed LDL. The results implied that rScllT-sepharose might be applicable in the isolation and purification of LDL from plasma.