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Open Access Research article

The evolution of the class A scavenger receptors

Fiona J Whelan1, Conor J Meehan2, G Brian Golding3, Brendan J McConkey4 and Dawn M E Bowdish1*

Author Affiliations

1 Department of Pathology and Molecular Medicine, McMaster University, 1200 Main Street West, Hamilton, L8N 3Z5, Ontario, Canada

2 Faculty of Biochemistry and Molecular Biology, Dalhousie University, 5080 College Street, Halifax, Nova Scotia, Canada, B3H 4R2

3 Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada

4 Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, N2L 3G1, Ontario, Canada

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BMC Evolutionary Biology 2012, 12:227  doi:10.1186/1471-2148-12-227

Published: 27 November 2012

Abstract

Background

The class A scavenger receptors are a subclass of a diverse family of proteins defined based on their ability to bind modified lipoproteins. The 5 members of this family are strikingly variable in their protein structure and function, raising the question as to whether it is appropriate to group them as a family based on their ligand binding abilities.

Results

To investigate these relationships, we defined the domain architecture of each of the 5 members followed by collecting and annotating class A scavenger receptor mRNA and amino acid sequences from publicly available databases. Phylogenetic analyses, sequence alignments, and permutation tests revealed a common evolutionary ancestry of these proteins, indicating that they form a protein family. We postulate that 4 distinct gene duplication events and subsequent domain fusions, internal repeats, and deletions are responsible for the diverse protein structures and functions of this family. Despite variation in domain structure, there are highly conserved regions across all 5 members, indicating the possibility that these regions may represent key conserved functional motifs.

Conclusions

We have shown with significant evidence that the 5 members of the class A scavenger receptors form a protein family. We have indicated that these receptors have a common origin which may provide insight into future functional work with these proteins.

Keywords:
Class A scavenger receptor; Innate immunity; Scavenger receptor; Pattern recognition receptor; Scavenger receptor cysteine rich domain; Comparative evolution