Building A Histidine

This parody (written by Greg Crowther) is sung to the tune of "Building A Mystery" (written by Sarah McLachlan and Pierre Marchand and performed by Sarah McLachlan).

Histidine is an amino acid -- one of about 20 found naturally in the human body. These amino acids can be linked together into long chains to form proteins. The process of manufacturing proteins out of amino acids is known as translation because a messenger RNA molecule is "translated" into a sequence of amino acids. This takes place at intracellular structures called ribosomes.

In humans, some amino acids can be made from scratch, while others must be supplied by one's diet. The latter are collectively known as "essential" amino acids. Histidine is one such essential amino acid, at least in rodents and human infants; there is some controversy as to whether adult humans can synthesize histidine.

This song tells the fictional story of an unspecified organism for whom histidine is in fact essential. The organism's enzymes, tired of having to obtain histidine from dietary sources, decide to make it themselves. Not surprisingly, they meet with little success.

Jargon advisory: each amino acid has a unique R group (also known as a functional group or side chain). The R group of histidine, technically known as an imidazole ring, has a pKa close to the normal pH of the cytoplasm, allowing it to buffer intracellular pH effectively. Ribose is a five-carbon sugar from which histidine is made. Globins are histidine-rich proteins such as hemoglobin and myoglobin.

It comes in your food; that's what the textbooks say.
But you can't be subdued until the next meal.
You've got some ribose and a few carbonyls,
And you're going to take a break from your normal routine....
You're building a histidine.

You live in a cell, where you sleep with organelles,
And you won't give up on the synthesis,
Though it's not going well.

The R group buffers you 'cause it has the perfect pKa;
Can you really create it
Without thermodynamics getting in the way?

It's not difficult to form these amino acids.
You're so clueless; maybe you need some classes....

'Cause you're working, building a histidine.
Hold on -- that looks like alanine.
Yeah, you're working, building a histidine
Like those you've seen in Science magazine.

You woke up screaming aloud:
"Pray for more histidine,
'Cause, without that guy, my globins will die!

"We can't make protein without imidazole rings.
The ribosomes just sit there; they can't do a thing."

It's not difficult to form this residue.
E. coli does it, so tell me, what's wrong with you?

'Cause you're working, building a histidine.
Hold on -- that's more like arginine.
Yeah, you're working, building a histidine
Like those you've seen in Science magazine.

Ooh, you're working, building a histidine.
Hold on -- that looks like tyrosine.
Yeah, you're working, building a histidine
Like those you've seen in Science magazine.

Yeah, you're working, building a histidine.
Hold on -- that's gotta be glutamine.
Oh yeah, you're working, building a histidine
Like those you've seen in Science magazine.

You're building a histidine.

• MP3 (by Jessica Raaum)