By Harold Baum
The primary sequence of proteins
Is coded within DNA
On sense strand of the double helix
Coiled antiparallel way.
(Introns and exons, changes post-transcriptional, and all
Glycosylations, don’t alter such basics at all)
DNA’s read 3 prime to 5 prime
Triplet permutations of base,
Variations occur at third place.
(A-T and G-C, the four deoxyribotides, besides
U-A and C-G, complement as nucleotides)
Now DNA acts as a template
For RNA polymerase
Transcribing the genetic message
But in antiparallel phase.
(5 prime to 3 prime, that’s the new message’s way, OK?
Encoded this time in new messenger RNA)
tRNA we now consider
With clover leaf multiple bend
Anticodon length at the bottom
Ad’nine at the free 3 prime end.
(From 3 to 5 now, so runs that coding base batch or patch,
Third bases somehow, can wobble a bit when they match)
tRNA now gets as loading
Amino acyl moiety
By way of enzyme-bound donor
Amyno acyl AMP.
(Enzyme selective, for each amino acyl load – its mode
Takes the respective tRNA with the right code).
The ribosome has two subunits
Differing somewhat in weight,
To start protein synthetic sequence
They firstly must dissociate.
(Eucaryotic, to 60 S and 40 S – unless
Procaryotic, which are similar but weigh less).
Methionine has an adaptor
That is, as its tRNA
A species with an anticodon
To code saying “please start this way”
(Met tRNA binds mRNA AUG, you see
Factors can now play their role aided by GTP)
They’re complexed all with small subunit
Then larger subunit locks in
Met tRNA on the P site
And translation now can begin.
(Next tRNA, with its amino acyl on, stuck on
Binds at the site A, at the very next codon along).
Mithionine now is transferred from
Ester binding on tRNA
To form a peptide bond with amino
Acyl group tagged on at site A.
(Messenger moves on, peptidyl adaptor to P, you see
Still on its codon, Met tRNA falls on free).
New loaded adaptor attaches
At A site, next bit of the code
Peptidyl now is transferred to
Amino of incoming load.
(Messenger in train, loads site P with thripeptidyl, in style
Frees site A again, to take next amino acyl).
Thus chain grows from end free amino
Specified by mRNA
Till there’s a termination message
Like UAG or UAA.
(Peptides when complete, released to their subsequent fate, they state
And when not replete, ribosomes will dissociate).
Translation requires many factors,
Break down GTP on the way,
Prokaryotics all start with
N-formyl Met t-RNA.
(On mRNA, translating in sequential train, again
Polysome array, makes replicates of the same chain).
Oh golly that was a long saga,
Oh gosh how the scansion was strained,
I’ve just sang this song to my bonnie,
No wonder my bonnie looks pained.
Bring back, oh bring back, oh bring back my text book to me, to me,
Bring back, oh bring back plain simple biochemistry.
P.S. Дорогой Босс. Прости, что не смогла прийти на твой день рождения. Надеюсь, ты на меня не обижаешься. Я очень люблю тебя.