Isolation and properties of a 23-KD haemolymph protein from the tsetse, Glossina morsitans morsitans

Abstract

The haemolymph of the tsetse, Glossina morsitans morsitans, contains a low molecular weight protein of very high density (1.29 g/mi). The protein was detected in the haemolymph during all developmental stages of the insect. Purification of the protein was achieved by a combination of density gradient ultracentrifugation and repeated gel permeation chromatography. Electrophoresis under non-denaturing and denaturing conditions showed the protein to be a single polypeptide chain (M,˜23,000). Amino acid analysis revealed a relatively high content of the acidic amino acids as well as serine and glycine. The protein contained lipids as shown by Sudan Black staining but was nonglycosylated. Using rabbit antiserum against the isolated protein in immunodiffusion and immunoblotting experiments, no cross-reactivity was detected with haemolymph samples from insects representing six orders. Although the function of the protein remains unknown, its uniqueness to Glossina suggests that it may have a role in the physiology of this insect.