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A is for ALANINE [poem]

by Greg Crowther


A is for ALANINE, three carbons long;
C is for CYSTEINE, with a sulfhydryl prong.
D is ASPARTATE; itís lost its H-plus;
GLUTAMATEís E; it too appears thus.

F, PHENYLALANINE: benzene on board;
GLYCINE, or G, wins the small-size award.
H is for HISTIDINE. What a great buffer!
And water prompts I, ISOLEUCINE, to suffer.

K: LYSINE's high on the pKa scale;
L is for LEUCINE, with its long Y-shaped tail.
M is METHIONINE: sulfury lout,
And N is ASPARAGINE: amide, no doubt.

P: PROLINE flaunts its odd ring like a bride;
Q, GLUTAMINE, is another amide.
R, ARGININE, has four Ns in all.
And S is for SERINE, a petite alcohol.

T is for THREONINE, similar to S;
V is for VALINE. Aliphatic? Why, yes!
W, TRYPTOPHAN: rings at the end,
And Y, TYROSINE, is the kinases' friend.

Which brings us right back to the start of the song:
A is for ALANINE, three carbons long.


This poem presents a brief review of amino acid abbreviations and structures. It was written in 1999, published in Biochemical and Molecular Biology Education (BAMBEd) in 2005, and revised in 2015.

Study questions: (1) Explain the lines describing histidine, isoleucine, and tyrosine. (2) A previous version of this poem included the following lines: "D is ASPARTATE, a good proton source,/ And E, GLUTAMATE, is one also, of course." In what way are these lines misleading? Answers: (1) Histidine has a pKa close to the normal pH of the cytosol and therefore is an effective intracellular buffer; the R group of isoleucine is hydrophobic; and many protein kinases add a phosphate at the -OH site of tyrosine. (2) Aspartate and glutamate are technically the names of the deprotonated amino acids, so, having already lost their protons, neither is a "good proton source" any longer.

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