In the current issue of Science there is an article by Ban et al that reports the 3D atomic
scale structure of the most complex object ever, the largest of the two subunits of a
ribosome. This thing is huge, 2.6 million daltons, more than 50 times as big as your
average protein. It has 3,000 nucleotides of RNA bent into a complex shape folded in
out and around 31 different interlocking proteins. I find this really interesting at a lot of
different levels. It's amazing they can find the 3D shape of something this big and complex.
The object itself is very important, ribosomes are where proteins are made. There are
practical implications, the ribosomes in bacteria are major target for antibiotics.
There are philosophical implications too.
Two-thirds of the mass of ribosome's comes from RNA, and it turns out that the RNA
is the catalyst for the protein synthesis, not the one third that is protein as you might
expect, the protein acts just as girders to hold the machine together. RNA can not only
store information like DNA it can also catalyze chemical reactions like proteins. RNA
acting as a enzyme had been noticed before but never at something this important or
fundamental to all life. It give support to the theory that when life first originated 4 billion
years ago it contained no DNA and no protein, just pure RNA.
John K Clark jonkc@att.net
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