Amyloid: journal of protein folding disorders vol:3 issue:3 pages:183-186
date:UNIV UTRECHT,DEPT VET PATHOL,UTRECHT,NETHERLANDS
We have previously immunologically typed amyloid protein extracted from a horse with malignant histiolymphocytic lymphosarcoma as immunoglobulin (Ig)-derived amyloid. In the present paper, the Ig character of the horse amyloid is confirmed by the amino acid sequence of the constituent protein. Its major component is identified as a 217-residue complete horse lambda light chain. On the basis of sequence homology, the variable (V) and joining (J) segments were most closely related to those encoded by the equine V lambda 2- and J lambda 1-gene families, respectively. Notably the constant (C) region, although most closely related to the C lambda 1-gene, differed from the prototypic sequence by five residues. These findings have provided further, evidence that proteolytic precleavage of the precursor is not essential in light-chain-associated (AL) amyloidogenesis. In addition to establishing the first complete amino acid sequence of a horse Ig light chain, the discovery of a unique C-region primary structure implies extensive C lambda 1 polymorphism or the existence of a heretofore unrecognized equine C lambda gene.