Characterization of Heme Lipoprotein in Ixodid Tick Saliva and Hemolymph

Abstract

This study characterized heme lipoprotein (HeLp), the most abundant protein in Ixodid tick hemolymph and saliva using a number of biochemical and molecular methods. This study revealed that HeLp is the most abundant protein in the hemolymph and saliva of all Ixodid ticks examined. Although highly conserved, the proteins are not identical among these species. HeLp is a heterodimer of homodimers, having the formula B2A2. The glycosylated HeLp-B subunit dimerizes with at least one intersubunit disulfide linkage. In both hemolymph and saliva, proteins appearing to be precursors occur in smaller titers. HeLp is translated as a single polypeptide precursor including a signal peptide, the HeLp-B sequence, a processing site, and HeLp-A sequence. The cDNA sequence reveals that HeLp is homologous to vitellogenin. A molecular model of HeLp-B was constructed; supporting our earlier studies and will be a useful tool for further studies.