Protein Syntheis, part 3


ribosomes don't know which AA's should come next in polypeptide,
so we need instructions on how to build a protein ...

The simplest solution would be to list the desired tRNA's
in order 5'-end to 3'-end as a messenger [mRNA].
However, due to hydrogen bonding sites as follows:

  • A has 2 sites
  • G has 3 sites
  • U has 2 sites
  • C has 3 sites,
    the RNA nucleotides pair as follows:
  • A pairs with U
  • G pairs with C
  • U pairs with A
  • C pairs with G
    Therefore, it becomes necessary to list the "opposite" of the desired tRNA,
    starting with the start AA, Met.
    From the Secret Decoder Ring, we know the tRNA code for Met is UAC,
    and the mRNA code would be AUG...
    ending with one of the terminating tRNAs {AUU, ACU, or AUC},
    whose mRNA code would be {...UAA, ...UGA, or UAG}

    A valid mRNA would begin & end:
    . . {AUG... ...UAA} or
    . . {AUG... ...UGA} or
    . . {AUG... ...UAG},
    and would then be 3(a+2) bases long,
    . . where a = number of AAs in protein,

    length of mRNA molecule
    protein AAs mRNA
    insulin, human 88 270 b
    myofibril, rabbit 250 756 b


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    © 2004 Prof. LaFrance, Ancilla College