IDENTIFICATION OF A NOVEL MEMBER OF THE PENTRAXIN FAMILY IN XENOPUS-LAEVIS

Pentraxins are a family of acute phase reactants. Two family members, C-reactive protein (CRP) and serum amyloid P component (SAP), are know n in a range of mammalian species. CRP and SAP are both about 200 resi dues long, and arose from a gene duplication event, apparently before the divergence of the mammalian orders. To elucidate the origins of ma mmalian pentraxins, we have searched for pentraxin-coding genes in the amphibian Xenopus laevis. We have identified a gene determining a pro tein (XL-PXN1) which is about twice the size expected: the XL-PXN1 gen e appears to be a fusion between regions encoding an amino-terminal pe ptide of unknown function and a carboxy-terminal pentraxin. The pentra xin domain is more divergent from CRP and SAP than they are from each other: it provides an outgroup for analysis of the evolution of mammal ian pentraxins and confirms that putative CRP and SAP proteins partly characterized in non-vertebrate species cannot be true homologues of t he mammalian proteins.