Protein

Related: https://en.wikipedia.org/wiki/Protein_(nutrient)

Usually noted D-something, L-something, e.g. L-alanine, D-glutamine.

The common ones.

The rare ones. Notably present in peptidoglycan.

How many "la"s does a name need to have?

Like cysteine, but with selenium instead of sulfur.

The weird one, not directly coded in the genetic code.

proteins also have a half-life, much like RNA. But it tends to be longer.

Protein dimer made up of two identical proteins, e.g. https://en.wikipedia.org/wiki/Fatty_acid_synthase

Of specific species:

The study of the proteome.

A protein that is a catalyst for some chemical reaction.

For an initial concrete example, consider e. Coli K-12 MG1655 gene thrA.

Forms the bacterial cell wall.

From the Wikipedia image we can see clearly the polymer structure formed: it is a mesh with:

Binds an amino acid to the correct corresponding tRNA sequence. Wikipedia mentions that humans have 20 of them, one for each proteinogenic amino acid.

The second protein to have its structure determined, after myoglobin, by X-ray crystallography, in 1965.

Breaks up peptidoglycan present in the bacterial cell wall, which is thicker in Gram-positive bacteria, which is what this enzyme seems to target.

Part of the inate immune system.

It is present on basically everything that mammals and birds excrete, and it kills bacteria, both of which are reasons why it was discovered relatively early on.

With X-ray crystallography by David Chilton Phillips. The second protein to be resolved fter after myoglobin, and the first enzyme.

Published at: Structure of Hen Egg-White Lysozyme: A Three-dimensional Fourier Synthesis at 2 Å Resolution (1965). The work was done while at the Davy Faraday Research Laboratory of the Royal Institution.

Phillips also published a lower resolution (6angstrom) of the enzyme-inhibitor complexes at about the same time: Structure of Some Crystalline Lysozyme-Inhibitor Complexes Determined by X-Ray Analysis At 6 Å Resolution (1965). The point of doing this is that it points out the active site of the enzyme.

https://www.nature.com/articles/206757a0 on Nature 181, 662-666. Paywalled as of 2022. Has some nice pictures in it.

https://www.nature.com/articles/206761a0 on Nature 206, 761-763. Paywalled as of 2022. Has some nice pictures in it.

From Wikipedia:

In humans, myoglobin is only found in the bloodstream after muscle injury.

Published at: a Three-Dimensional Model of the Myoglobin Molecule Obtained by X-Ray Analysis (1958). The work was done at the Cavendish Laboratory.

https://www.nature.com/articles/181662a0 on Nature. Paywalled as of 2022.