Gene conversion among chemokine receptors

It has been proposed that proteins which are involved in host defence and s usceptibility undergo accelerated evolution. Chemokine receptors have roles as pro-inflammatory agents acting in response to infection: and in additio n are receptors for entry of viruses and other pathogens into cells. Consis tent with this, their rate of evolution is higher than that for other membe rs of the seven-transmembrane domain receptor family. The pattern of evolut ion of the chemokine receptors was examined in detail. Both chromosomal clu sters of chemokine receptors (CC and CXC) showed evidence of a number of ge ne conversions. These are likely to have resulted in protein sequence chang es, which could possibly alter function. 45% of a control group of clustere d genes also showed evidence of conversion. Thus, the fixation of a gene co nversion is not in itself sufficiently unusual in tandemly repeated genes a nd cannot be taken as strong evidence of a selection for a novel function. However, the degree of amino acid difference between the chemokine receptor s CCR1 and CCR3 was greater than that for any of the control genes. Such ch anges could have functional implications for inter-species differences in c hemokine receptor interactions with pathogens. (C) 2000 Elsevier Science B. V. All rights reserved.