人源fidgetin like-1蛋白AAA结构域的重组表达及酶学性质分析

Recombinant expression and activity analysis of the AAA domain of human fidgetin like-1

Fidgetin是2000年发现的一个AAA蛋白家族新成员,同源序列分析表明它与ka-tanin、spastin属于AAA家族的同一亚家族,因此可能也具有ATP依赖的微管切割活性,ATP的结合和水解应该发生于fidgetin蛋白中保守的AAA结构域.在大肠杆菌中重组表达的人源fidgetin like-1(FIGL-1)蛋白的AAA结构域片段(HsFIGL-1-AAA),纯化后的最终产率为每升5 mg蛋白.与AAA蛋白通常形成六聚体不同,HsFIGL-1-AAA在溶液中为单体,且其ATPase活性很低,仅为0.0063 s-1.与其他AAA蛋白的序列比对发现,Sensor 2 motif中保守的Arg残基在HsFIGL-1-AAA结构域中为Thr,但该位点的突变T609R并未明显改变该蛋白的ATPase活性.这些结果提示HsFIGL-1可能以一种特殊的方式发挥功能,这为进一步研究fidgetin及其同源蛋白的结构和功能奠定了基础.

Fidgetin is a new AAA protein cloned in 2000, because it has an AAA domain at its C - terminus. Together with two microtubule-severing proteins katanin and spastin, fidgetin is classified into subfamily -7 of AAA family, which implies that ridgetin may have ATP - dependent mierotubule - severing activity and that the conserved AAA domain is responded for the ATP binding and hydrolysis. In order to understand the activity of its AAA domain, the AAA domain of human fidgetin like - 1 （ HsFIGL - 1 - AAA） was expressed in E. coli with a yield of 5 mg/L after the purification of affinity chromatography and ion-exchange chromatography. The result of size exclusion chromatography shows that HsFIGL - 1 -AAA is a monomer, which is dramatically different from the behavior of other AAA proteins. The basal ATPase activity of HsFIGL - 1 - AAA is as low as 0. 0063 s^ - 1. Sequence comparison shows that the conserved Arg in Sensor 2 motif, which was found to be important for ATP binding and hydrolysis in some AAA proteins, is replaced by Thr in HsFIGL - 1. However, the mutantation of this Thr residue into Arg, T609R, does not change the ATPase activity of this protein. These results indicate that HsFIGL - 1 may function in a distinct way. These pave the way for further structural and functional study of this protein.