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An Antifreeze Glycopeptide Gene from the Antarctic Cod Notothenia coriiceps neglecta Encodes a Polyprotein of High Peptide Copy Number

Ku-Chuan Hsiao, Chi-Hing C. Cheng, Indira E. Fernandes, H. William Detrich and Arthur L. DeVries
Proceedings of the National Academy of Sciences of the United States of America
Vol. 87, No. 23 (Dec., 1990), pp. 9265-9269
Stable URL: http://www.jstor.org/stable/2355802
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
An Antifreeze Glycopeptide Gene from the Antarctic Cod Notothenia coriiceps neglecta Encodes a Polyprotein of High Peptide Copy Number
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Abstract

The antarctic fish Notothenia coriiceps neglecta synthesizes eight antifreeze glycopeptides (AFGP 1-8; Mr 2600-34,000) to avoid freezing in its ice-laden freezing habitat. We report here the sequence of one of its AFGP genes. The structural gene contains 46 tandemly repeated segments, each encoding one AFGP peptide plus a 3-amino acid spacer. Most of the repeats (44/46) code for peptides of AFGP 8; the remaining 2 code for peptides of AFGP 7. At least 2 of the 3 amino acids in the spacers could act as substrate for chymotrypsin-like proteases. The nucleotide sequence between the translation initiation codon (ATG) and the first AFGP-coding segment is G+T-rich and encodes a presumptive 37-residue signal peptide of unusual sequence. Primer extension establishes the transcription start site at nucleotide 43 upstream from ATG. CAAT and TATA boxes begin at nucleotides 53 and 49, respectively, upstream from the transcription start site. The polyadenylylation signal, AATAAA, is located ≈ 240 nucleotides downstream from the termination codon. A mRNA (≈ 3 kilobases) was found that matches the size of this AFGP gene. Thus, this AFGP gene encodes a secreted, high-copy-number polyprotein that is processed posttranslationally to produce active AFGPs

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