Expression and characterization of Guamerin, an elastase inhibitor in Escherichia coli

Abstract

Guamerin, a cysteine-rich protein from the Korean leech Hirudo nipponia, is a potent inhibitor of elastase. The guamerin encoding gene was obtained by polymerase chain reaction and expressed in Escherichia coli under the control of T7lac promoter by using a pET22b vector, which has a pelB leader sequence and a 6 X Histidine tag at the N-terminal and C-terminal regions, respectively. Recombinant guamerin was purified using His$\cdot$Bind affinity column and reverse-phase high pressure liquid chromatography. N-terminal amino acid sequence analysis, compostion analysis and electrospray ionization mass spectrometry confirmed that recombinant guamerin had correctly processed N-terminus, expected amino acid sequence and molecular mass. The activity of recombinat guamerin was very similar to that of native protein. Double reciprocal plotting showed that the recombinant guamerin had inhibition constant of $8.8 \times 10^{-9}$ M against elastase, which is comparable to native guamerin. Recombinant guamerin formed a protease-inhibitor complex which was demonstrated by gel permeation chromatography. The recombinant guamerin may provide a useful tool for the evaluation of the elastase inhibitory mechanism and for treating various inflammatory human diseases .