The identification and characterization of lysozyme from the hard tick Haemaphysalis longicornis

A full-length cDNA-encoding lysozyme was obtained from cDNA libraries of salivary glands of the hard tick Haemaphysalis longicomis and designated as HILysozyme. The HILysozyme sequence represents an open reading frame for a putative signal peptide and the mature protein composed of 121 amino acids. The calculated molecular weight of the protein is 13.7 kDa, and the theoretical isoelectric point is 9.85. HILysozyme shares 41-79% amino acid sequence identity with the lysozymes of other organisms. The activity of recombinant HILysozyme expressed in Escherichia coli was confirmed by a lytic zone assay using lyophilized Micrococcus lysodeikticus. The HILysozyme activity decreased at 70 C and was demonstrated at acidic side and neutral in a pH range. Elevated gene expression of HILysozyme was observed when female ticks were challenged with bacteria, suggesting possible roles of lysozyme as an innate immunity of ticks against microorganisms. (C) 2010 Elsevier GmbH. All rights reserved.