The complete amino acid sequence of growth hormone and partial amino acid sequence of prolactin and somatolactin from sea perch (Lateolabrax japonicus)

Growth hormone (GH), prolactin (PRL) and somatolactin (SL) were purified si multaneously under alkaline condition (pH 9.0) from pituitary glands of sea perch (Lateolabrax japonicas) by a two-step procedure involving gel filtra tion on Sephadex G-100 and reverse-phase high-performance liquid chromatogr aphy (rpHPLC). At each step of purification, fractions were monitored by so dium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and by i mmunoblotting with chum salmon GH. PRL and SL antisera. The yields of sea p erch GH, PRL and SL were 4.2, 1.0 and 0.28 mg/g wet tissue, respectively. T he molecular weights of 19,200 and 20,370 Da were estimated by SDS-PAGE for sea perch GH and PRL, respectively. Two forms of sea perch SL were found: one (28,400 Da) is probably glycosylated, while the other one (23,200 Da) i s believed to be deglycosylated. GH bioactivity was examined by an in vivo assay. Intraperitoneal injection of sea perch GH at a dose of 0.01 and 0.1 mug/g body weight at 7-day intervals resulted in a significant increase in body weight and length of juvenile rainbow trout. The complete sea-perch GH amino acid sequence of 187 residues was determined by sequencing fragments cleaved by chemicals and enzymes. Alignment of sea-perch GH with those of other fish GHs revealed that sea-perch GH is most similar to advanced marin e fish, such as tuna, gilthead sea bream, yellowfin porgy, red sea bream, b onito and yellow tail with 98.4, 96.2%, 95.7%, 95.2%, 94.1% and 91% sequenc e identity, respectively. Sea-perch GH has low identity to Atlantic cod (76 .5%), hardtail (73.3%), flounder (68.4%), chum salmon (66.3%), carp (54%) a nd blue shark (38%). Partial amino-acid sequences of 127 of sea-perch PRL a nd the N-terminal of 16 amino-acid sequence of sea-perch SL have been deter mined. The data show that sea-perch PRL has a slightly higher sequence iden tity with tilapia PRL( 73.2%) than with chum salmon PRL(70%) in this 127 am ino-acid sequence. (C) 2001 Elsevier Science B.V. All rights reserved.