Elephantfish proinsulin possesses a monobasic processing site.

M A Gieseg; P A Swarbrick; L Perko; R J Powell; J F Cutfield

doi:10.1006/gcen.1997.6965

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Elephantfish proinsulin possesses a monobasic processing site.

M A Gieseg·P A Swarbrick·L Perko·R J Powell·J F Cutfield

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Abstract

Total pancreatic RNA from the holocephalan species Callorhyncus milii (elephantfish) was used to make cDNA as a template for the polymerase chain reaction. Three redundant primers based on the known amino acid sequence of elephantfish insulin were used to amplify a fragment of proinsulin comprising truncated B-chain, complete C-peptide, and complete A-chain. Whereas the C-peptide/A-chain junction contained the expected dibasic cleavage site (-Lys-Arg-), the B-chain/C-peptide junction was found to contain only a single Arg, the first such site to be unequivocally associated with the proteolytic processing of a proinsulin to insulin. Examination of the flanking sequences around this site shows that a typical endocrine/neuroendocrine PC3 conversion enzyme should still be able to cleave, as the general requirements for precursor processing at a monobasic site are satisfied, notably a basic residue (Lys) at the -4 position. An acidic residue (in this case Asp) at the +1 position, which is seen in all known proinsulins, is maintained. The corresponding genomic DNA fragment of elephantfish proinsulin was also amplified by PCR, revealing a 402-bp intron at the conserved IVS-2 position within the C7 codon.

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Amino Acid Sequence Animals Base Sequence Binding Sites C-Peptide DNA DNA, Complementary Fishes Molecular Sequence Data Pancreas Polymerase Chain Reaction Proinsulin RNA Sequence Homology Templates, Genetic Comparative Study Journal Article Research Support, Non-U.S. Gov't

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M A Gieseg, P A Swarbrick, L Perko, R J Powell, J F Cutfield. 1997. Elephantfish proinsulin possesses a monobasic processing site.. https://doi.org/10.1006/gcen.1997.6965

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