The Protein Man's Blog | A Discussion of Protein Research

  Poly-histidine tagged proteins account for more than 90% of routine recombinant protein expression and purification. Histidine tag has many advantages over other affinity tags such as small size, high affinity for binding to IMAC resins (Immobilized metal affinity chromatography) and allows one step purification of recombinant protein. But sometimes a histidine tagged protein doesn’t bind to the affinity column and evades it’s capture and subsequent purification. Although such instances are not very common but can be very frustrating whenever they happen. However, there are ways to troubleshoot if such a problem arises and the solutions are discussed below in a step by step manner.

Cysteine is one of the most reactive amino acid residue owing to the thiol (-SH) group, thiols can serve as an electron donor in different reactions. Cysteine thiols can form part of catalytic centre and can frequently participate in enzymatic reactions, not just that, cysteine thiols can also undergo a variety of covalent post-translational modifications (PTMs) and formation of disulphide bonds. The thiol modifications can act as important mediators of redox signalling and protein function regulation.