Answer to Question #297841 in Human Anatomy and Physiology for Amir

Question

In the chain of ribonuclease of pancreas one of polypeptides has the following amino acids:

lysine-asparaginicacid-glycine-threonine-asparaginicacidglutaminicacid-cysteineYoushalldetermine

mRNA controlling the synthesis of the mentioned polypeptide.

Answer 1

Glucagon is a 29-amino-acid pancreatic hormone that regulates glucose metabolism, while glicentin is a 69-amino-acid intestinal peptide that comprises the glucagon sequence flanked by peptide extensions at the amino and carboxy termini. The glucagon gene produces a precursor peptide that contains glucagon as well as two other structurally related glucagon-like peptides separated by a peptide. Exons that code for these peptides are separated. We employed antisera against synthetic glucagon-like peptides and exon-specific, complementary oligonucleotides to analyze proteins and mRNAs in pancreatic and intestinal extracts to see if the pancreatic and intestinal versions of glucagon arise from different RNA and/or protein processing. Preproglucagon mRNAs are identical in both organs, but distinct and very specific peptides are liberated.Immunocytochemistry shows colocalization of glucagon and the two glucagon-like peptides in identical cells.