Jellyfish Sleep, The Most Abundant Natural Molecule On The Planet, and BONCAT (with a bonus on Mitochondria)

Today I Learned:
1) Jellyfish (at least one species, Cassiopea, the upside-down jellyfish) sleep.

2) Think for a second on the following question: what is the most abundant natural product (molecule) on the planet? The answer, I learned today, is probably “hopanoids”. Hopanoids are a class of steroid(!) used in plasma membranes by a number of bacterial species, and are important in not-entirely-clear ways for bacteria/plant interactions. They’re found in *vast* quantities in any kind of sedimented, biologically-produced material.

3) …the scientific technique “BONCAT”, for “BioOrthogonal Non-Canonical Amino acid Tagging. It’s a rather sophisticated way to accurately measure the quantities of specific proteins in a biological sample (say, a bacterial culture or cell culture or mouse embryo). For those interested, it works by… well, this isn’t going to fit in one sentence.

You basically replace the methionines in a cell’s proteome with a non-natural amino acid called azidohomoalanine (Aha), which seems to be functionally nearly identical to methionines BUT has the side-chains necessary for click-chemistry. Ridiculously enough, you can do this by simply replacing methionine in the cells’ media with azidohomoalanine. Then you can lyse the cells, click the proteins onto click-compatible biotin, purify it out with streptavidin, and do whatever you want to it (usually mass-spec, using a spiked heavy-isotope version as a control to give absolute quantitation).

4) This was a heavy-learning day, so y’all get a fourth fact. Actually a constellation of related facts… about mitochondria!

Most mitochondria in most eukaryotes have thirteen protein-coding genes (with rare variation of one or two genes) on a single circular chromosome (with tens to hundreds of copies per mitochondria). Some protists, however, have mitochondria with *linear* DNA, which has its own distinct form of telomere at the ends. Bizarrely but not surprisingly, plant mitochondrial genomes are often very large (there’s a 2.5 Mb plant mitochondrial genome), even though they contain the same genes as all the other eukaryotes. Oh, and cucumbers have three distinct mitochondrial genomes in every mitochondria. Cucumber genetics is weird.

Last but not least, there are eukaryotes with no mitochondria at all! They’re basically all obligate parasites, including Giardia, which explains how they’re able to get away with not having mitochondria.