Expression of soluble human Neonatal Fc-receptor (FcRn) in Escherichia coli through modification of growth environment

Neonatal Fc-receptor (FcRn) with its affinity to immunoglobulin G (IgG) has been the subject of many pharmacokinetic studies in the past century. This protein is well known for its unique feature in maintaining the circulating IgG from degradation in blood plasma. FcRn is formed by non-covalent association between the alpha-chain with the beta-2-microglobulin (beta 2m). Many studies have been conducted to produce FcRn in the laboratory, mainly using mammalian tissue culture as host for recombinant protein expression. In this study, we demonstrate a novel strategy to express the alpha-chain of FcRn using Escherichia coli as the expression host. The expression vector that carries the cDNA of the alpha-chain was transformed into expression host, Rosetta-gami 2 strain for inducible expression. The bacterial culture was grown in a modified growth medium which constitutes of terrific broth, sodium chloride (NaCl), glucose and betaine. A brief heat shock at 45 degrees C was carried out after induction, before the temperature for expression was reduced to 22 degrees C and grown for 16 h. The soluble form of the alpha-chain of FcRn expressed was tested in the ELISA and dot blot immunoassay to confirm its native functionality. The results implied that the alpha-chain of FcRn expressed using this method is functional and retains its pH-dependent affinity to IgG. Our study significantly suggests that the activity of human FcRn remain active and functional in the absence of beta 2m. (C) 2016 Elsevier Inc. All rights reserved.