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Primary structures of the alanine-rich antifreeze polypeptides from grubby sculpin, Myoxocephalus aenaeus

1988; NRC Research Press; Volume: 66; Issue: 2 Linguagem: Inglês

10.1139/z88-057

1480-3283

Avijit Chakrabartty, Choy L. Hew, Margaret A. Shears, Garth Fletcher,

Neurobiology and Insect Physiology Research

Antifreeze polypeptides (AFP) isolated from the plasma of the grubby sculpin (Myoxocephalus aenaeus)were compared with those of a close relative, the shorthorn sculpin (Myoxocephalus scorpius). Both species synthesize a family of AFP that are alanine rich and exist as amphiphilic α-helices. The grubby sculpin AFP could be resolved into five active components by reverse-phase liquid chromatography. The major (GS-5) and one of the minor (GS-8) components were sequenced. Grubby sculpin AFP GS-5 was 33 amino acids long. It was homologous to one of the minor shorthorn sculpin AFP (SS-3) in terms of its molecular size and amino acid sequence. The sequences of these two components differed by only four amino acids. The minor grubby sculpin AFP GS-8 was 40 amino acids long. It was shorter than the major shorthorn sculpin AFP (SS-8) by five amino acids. The sequence of the first 40 amino acids from SS-8 and GS-8 was essentially identical, differing by only 4 amino acids. Antibodies raised against SS-8 cross reacted with GS-8 but not with the shorter AFP (GS-5 and SS-3). The data suggest that the antibody was directed towards the unstructured N-terminal regions of SS-8 and GS-8. It would appear that shorthorn and grubby sculpins possess similar families of AFP genes and that the grubby sculpin preferentially expresses one gene product (GS-5) while the shorthorn sculpin expresses another, larger product (SS-8).