V. Lund et Ja. Olafsen, ATYPICAL PHOSPHORYLCHOLINE-REACTIVE PROTEIN FROM ATLANTIC SALMON, SALMO-SALAR L, Comparative biochemistry and physiology. B. Comparative biochemistry, 119(3), 1998, pp. 471-477
A phosphorylcholine-reactive protein was isolated from serum of Atlant
ic salmon (Salmo salar, L.) by affinity chromatography on a phosphoryl
choline-conjugated Sepharose column followed by elution with phosphory
lcholine. Based on the method used we describe the isolated protein as
salmon phosphorylcholine-reactive protein (salmon PRP). Salmon PRP ha
s calcium-independent binding to phosphorylcholine. The protein exists
in a monomeric and dimeric form with molecular weight of approximatel
y 80 and 160 kD, respectively. Separation of the protein preparation o
n SDS-PAGE under reducing conditions resulted in disappearance of the
80 and 160 kD bands and appearance of a major protein band of approxim
ately 100 kD. The N-terminal amino acid sequences of the non-reduced 8
0 and 160 kD bands and the reduced 100 kD band were identical. Apart f
rom the dimeric form, the molecular weight of salmon PRP and its appea
rance on SDS-PAGE is similar to human plasminogen. Comparison of the s
equence in a protein database resulted in approximately 50% identity w
ith human and bovine plasminogen. In addition, cross-reactivity betwee
n antibodies to human plasminogen and salmon PRP was demonstrated. Thu
s, salmon PRP appears to be different from other phosphorylcholine-rea
ctive proteins which are mostly reported to be CRP-like proteins with
calcium-dependent binding to phosphorylcholine, pentameric ring-struct
ure and sequence homology between species. Whether salmon PRP is a new
type of phosphorylcholine-binding protein with an unknown function or
a plasminogen-like protein with binding specificity for phosphorylcho
line calls for further investigation. (C) 1998 Elsevier Science Inc. A
ll rights reserved.