Formation of Insulin (C254H377N65O75S6 )
                                         Mol.Wt : 5734Da
Preproinsulin   ------>Proinsulin ---------------> Insulin
(110 amino acids)     (86 amino acids)    (51 amino acids)
(signal peptide-24AA)  (B-chain 30 AA)                (C-chain 35AA)          (A-chain 21AA)  [AA-amino acid]

Preproinsulin Primary Structure -Schematic
Signal peptide helps preproinsulin to enter secretion pathway but during translation it is      cleaved off
leaving behind proinsulin with amino group attached to B-chain at one end and -COOH group attached
to A -chain at the other end with C-chain in between.Hydrophobicity of signal peptide helps in transport
of the nascent chain through microsomal membrane of Rough Endoplasmic Reticulum.
               (B-chain 30 AA)                (C-chain 35AA)          (A-chain 21AA)

proinsulin Primary Structure -Schematic
In proinsulin,the B-chain & A-chain are connected by C-peptide flanked by 2 pairs of basic amino
acids,Arg-Arg at B-end & Lys-Arg at A-end.

                                                              ( Primary structure of C-peptide }

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