Question

A chain GIVEQCCASVCSLYQLENYCN B chain FVNQHLCGSHLVEALYLVCGERGFFYTPKA Shown above is the amino acid sequence of the hormone insulin. This structure was determined by Frederick Sanger and his coworkers. Most of this work is described in a series of articles published in the Biochemical Journal from 1945 to 1955. When Sanger and colleagues began their work in 1945, it was known that insulin was a small protein consisting of two or four polypeptide chains linked by disulfide bonds. Sanger and his coworkers had developed a several methods for studying protein sequences, outlined below: Treatment with FDNB, FDNB (1-fluoro-2,4-dinitrobenzene) reacted with free amino (but not amido or guanidino) groups in proteins to produce dinitrophenyl (DNP) derivatives of amino acids: Acid Hydrolysis. Bolling a protein with 10% HCl for several hours hydrolyzed all of its peptide and amide bonds. Short treatments produced short polypeptides; the longer the treatment, the more complete the breakdown of the protein into its amino acids. Oxidation of cysteines. Treatment of a protein with performic acid cleaved all the disulfide bonds and converted all Cys residues to cysteic acid residues. Click Save and Submit to save and submit. Click Save All Answers to save all answers Save All Answ

Answer 1

Answer I:)

The alpha-amino groups are free in terminal amino acids. FDNB can bind to the free amino group. Phenylalanine and glycine have only alpha-amino groups and Sanger found that alpha-DNP-glycine and alpha-DNP-phenylalanine are formed. That is why the N-terminal should have these two amino acids.

Answer II:)

Yes, the known structure of insulin is also had Phenylalanine and glycine at the individual N-terminus of peptides. That is why Sanger’s result complies with that.

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