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Eppin has two potential protease inhibitory domains: a whey acid protein or four disulfide core domain and a Kunitz domain. The protein is also reported to have antibacterial activity against Gram-negative bacteria. Eppin and its whey acid protein and Kunitz domains were expressed in Escherichia coliand their ability to inhibit proteases and kill bacteria compared. | ễFEBS Journal Functional domains of the human epididymal protease inhibitor eppin Maelíosa T. C. McCrudden1 2 3 Tim R. Dafforn4 David F. Houston1 2 Philip T. Turkington2 and David J. Timson1 1 Schoolof BiologicalSciences MedicalBiology Centre Queen s University Belfast UK 2 Schoolof Chemistry and ChemicalEngineering Queen s University Belfast UK 3 Schoolof Medicine and Dentistry Queen s University Belfast UK 4 Schoolof Biosciences The University of Birmingham Edgbaston UK Keywords antibacterial protein elastase Kunitz domain respiratory uncoupling WAP domain Correspondence D. J. Timson Schoolof BiologicalSciences Queen s University Belfast MedicalBiology Centre 97 Lisburn Road Belfast BT9 7BL UK Fax 44 28 9097 5877 Tel 44 28 9097 5875 E-mail d.timson@qub.ac.uk Received 13 December 2007 revised 11 January 2008 accepted 11 February 2008 doi 10.1111 j.1742-4658.2008.06333.x Eppin has two potential protease inhibitory domains a whey acid protein or four disulfide core domain and a Kunitz domain. The protein is also reported to have antibacterial activity against Gram-negative bacteria. Eppin and its whey acid protein and Kunitz domains were expressed in Escherichia coli and their ability to inhibit proteases and kill bacteria compared. The Kunitz domain inhibits elastase EC 3.4.21.37 to a similar extent as intact eppin whereas the whey acid protein domain has no such activity. None of these fragments inhibits trypsin EC 3.4.21.4 or chymotrypsin EC 3.4.21.1 at the concentrations tested. In a colony forming unit assay both domains have some antibacterial activity against E. coli but this was not to the same degree as intact eppin or the two domains together. When bacterial respiratory electron transport was measured using a 2 3-bis 2-methoxy-4-nitro-5-sulfophenyl -2H-tetrazolium-5-carboxanilide assay eppin and its domains caused an increase in the rate of respiration. This suggests that the mechanism of cell killing may be partly through the permeablization of the .
