The dual role of ubiquitin-like protein Urm1 as a protein modifier and sulfur carrier

The ubiquitin-related modifier Urm1 can be covalently conjugated to lysine residues of other proteins, such as yeast Ahp1 and human MOCS3, through a mechanism involving the E1-like protein Uba4 (MOCS3 in humans). Similar to ubiquitination, urmylation requires a thioester intermediate and forms isopeptide bonds between Urm1 and its substrates. In addition, the urmylation process can be significantly enhanced by oxidative stress. Recent findings have demonstrated that Urm1 also acts as a sulfur carrier in the thiolation of eukaryotic tRNA via a mechanism that requires the formation of a thiocarboxylated Urm1. This role is very similar to that of prokaryotic sulfur carriers such as MoaD and ThiS. Evidence strongly supports the hypothesis that Urm1 is the molecular fossil in the evolutionary link between prokaryotic sulfur carriers and eukaryotic ubiquitin-like proteins. In the present review, we discuss the dual role of Urm1 in protein and tRNA modification.

Cloning, expression and purification of inhA from mycobacterium tuberculosis / 中华传染病杂志

Objective To clone and express inhA gene from mycobacterium tuberculosis , and purify the inhA protein. Methods Recombinant plasmid pET 24b/inhA was constructed and transferred into Escherichia coli . After restriction enzyme analysis and sequencing, the host bacteria were induced by IPTG and the product was identified by SDS PAGE. Furthermore, the overexpressed inhA protein was purified by Nit NTA Superflow system. Results The inhA gene was overexpressed in E. coli, the production was corresponding to 30 percent of total cell protein. Using Nit NTA Superflow,we can get more than 99% purified protein. Conclusions The cloning, expression and purification of inhA gene are successful.