Bacterially expressed rat retinol-binding protein is functional for retinol and transthyretin bindings

Retinol-binding protein (REP) was expressed in Escherichia coli using the cDNA for rat REP, and characterized. The expressed REP was fused to maltose-binding protein (MBP) at the N-terminal end (MBP-RBP), and MBP was enzymatically removed from the MBP-RBP with proteinase factor Xa. The binding of retinol and transthyretin (TTR) to the recombinant REP was monitored by means of gel filtration. The recombinant REP specifically bound to retinol with an affinity similar to that of purified REP from rat serum. Furthermore, the retinol-bound recombinant REP formed hetero-complexes with TTR similar to REP. Thus, the results showed that the recombinant REP expressed in E. coli is as functional as serum REP in terms of retinol and TTR bindings.