The novel sequences of major plasma apolipoproteins in the eel Anguilla japonica

cDNAs encoding major plasma apolipoproteins (apo) were cloned from the eel Anguilla japonica liver and their nucleotide sequences determined. Sodium d odecyl sulfate-polyacrylamide gel electrophoresis revealed that eel lipopro teins contain apolipoproteins of 28 kDa and 14 kDa as major components. Eac h of the two apolipoproteins showed two isoforms having different isoelectr ic points as demonstrated by two-dimensional electrophoresis. The two 28 kD a components had different N-terminal amino acid sequences, whereas the two 14 kDa components had an identical one. Then cDNA clones encoding these ap olipoproteins were isolated from a cDNA library constructed from the eel li ver. An acidic 28 kDa component (28 kDa-1) consisted of 259 amino acids inc luding a putative signal peptide of 27 residues, whereas a basic 28 kDa com ponent (28 kDa-2) was composed of 260 amino acids containing a putative sig nal peptide of 23 residues. The tandem repeating units, which are character istic of apolipoproteins, for 28 kDa-l showed 27.8% identity to that of por cine apoA-IV, although mammalian apoA-IV is about 40 kDa and much larger th an 28 kDa-l. However, the repeating units of 28 kDa-2 showed 52.5% identity to that of Atlantic salmon apoA-I. The 14 kDa apolipoprotein consisted of 142 amino acids containing a putative signal peptide of 20 residues. It has a novel sequence differing from apolipoproteins of other vertebrates. The transcriptional expressions of 28 kDa-l, 28 kDa-2., and 14 kDa components w ere all restricted to the liver, except for the transcripts of 28 kDa-2 whi ch were also slightly expressed in the intestine. (C) 2001 Elsevier Science B.V. All rights reserved.