Characterization of an antifreeze glycopeptide gene from the Antarctic cod, Notothenia neglecta, and a functional study of the "pre-" sequence of this antifreeze glycopeptide

• Main Author: Hsiao, Ku-Chuan
• Other Authors: DeVries, Arthur L.
• Format: Text
• Language: English
• Published: 1990
• Subjects: Biology; Molecular; Animal Physiology; Agriculture; Fisheries and Aquaculture; Antarctic; The Antarctic; Triplets; Antarc*
• Online Access: http://hdl.handle.net/2142/21291

The antarctic fish, Notothenia neglecta, synthesizes a series of 8 different-sized antifreeze glycopeptides (AFGP 1 to 8) which lower the freezing point of its body fluids below that of sea water. I report here the sequence of one of its AFGP genes. The structural gene contains 46 tandemly repeated segments, each coding for one mature peptide. Most of the repeats (44) are composed of 51 nucleotides and encode peptides of the AFGP 8 class, but the remaining two are longer (60 nucleotides each) and code for peptides of the AFGP 7 types. Separating each repeat are three triplets that code for amino acid residues that are absent in the mature peptides. The expressed nucleotide sequence between the initiation codon and the first AFGP-coding segment is GT-rich and codes for a presumptive hydrophobic signal peptide of unusual sequence (including a long stretch of alternating cysteine and valine residues). This presumptive signal peptide can be partially cleaved in an in vitro processing system. Putative CCAAT and TATA boxes begin 102 and 92 nucleotides, respectively, upstream from the initiation codon, and the polyadenylation signal, AATAAA, is located approximately 240 nucleotides downstream from the termination codon. Thus this AFGP gene appears to encode a secreted, high-copy-number polyprotein that is processed post-translationally to produce active AFGP.