Sunday, September 23, 2007

Selenocysteine and Pyrrolysine

More a postscriptum than a real post, but isn't it amazing, how selenocysteine and pyrrolysine, the 21st and 22nd proteinaceous amino acids, fit into the 2-1-3 genetic code scheme?

Selenocysteine (Sec / U): mRNA codon UGA. Related to cysteine, is in the same subgroup as tryptophane and cysteine and is in the same group as serine.

Pyrrolysine (Pyl / O): mRNA codon UAG. Consisting of a lysine backbone and a pyrrol ring containing a pi electron pair just as in tyrosine, histidine, tryptophane and phenylalanine, is in the same subgroup as tyrosine, and in the same group as histidine and lysine.

It's almost spooky, don't you think?

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