The role of salivary lipocalins in blood feeding by Rhodnius prolixus

Abstract

In order to overcome host mechanisms that prevent blood loss, the blood-sucking bug Rhodnius prolixus has evolved a complex salivary secretion containing dozens of different proteins. A number of these have been characterized and found to have roles in inhibiting various hemostatic or inflammatory systems. Interestingly, many of these biologically active salivary proteins belong to the lipocalin protein family. A proliferation of lipocalin genes has occurred via gene duplication and subsequent divergence. Functional genomic, proteomic, and functional studies have been performed to probe the role of salivary lipocalins in blood feeding. In the course of these investigations, anticoagulant, antiplatelet, antiinflammatory, and vasodilatory molecules have been described.

Figure 1

A. Clustal amino acid alignment and phylogenetic tree of lipocalins belonging to the nitrophorin (NP) group in R. prolixus saliva. Cysteine residues are highlighted in black, while other conserved regions are highlighted in gray. The original four NPs are labeled NP1-4. New NP sequences identified as ESTs are given the prefix RP. The biogenic amine binding protein is identified as BABP. B. A phylogenetic tree showing relationships within the nitrophorin group. The numbers refer to the bootstrap value for 1000 iterations (Taken from Ribeiro and others 2004).

Figure 2

Ribbon diagram of NP4 with the eight β-strands labeled A-H. Note the heme prosthetic group located in the central cavity (From Andersen and others 1998).