The Evolution of Adenine Synthesis

3-D Structure of Several Key Enzymes

The protein data bank houses a database which contains the 3-D structures of many proteins. All of the proteins involved in adenine synthesis can be found in this online database.

Another program called CONSURF will accept a protein database entry as input and generate a script that can be used to color the amino acids by their variability. The default of this program is to color highly conserved amino acids as shades of purple and weakly conserved amino acids as blue and white. The script so generated was modified so that all of the purple atoms appear as a shade of gray. Blue and off white were also modified to appear as white. The modifications were necessary so that the images would print correctly in black and white. The modified script was used to color several of the enzymes used in the synthesis of adenine (figures 13.2 - 13-5).

The black and gray regions in the following figures are regions of high conservation. These regions contain most of the information. Between twenty to thirty percent of the amino acids found in these proteins belong to a highly conserved region. In these regions, the knowledge per amino acid should be similar to that of insulin.

In chapter 5, because of the side reactions that are possible in the primordial soup, 2 bits of information are assigned to every amino acid that is used by life. So the white regions of the proteins in the following figures must contribute at least 2 bits of information, and in this special case, because natural selection is not yet active, the information and knowledge are additive. Therefore, the total can be related to a probability (see chapter 5).

Figure 13.2: Amidophosphoribosyl Transferase (474 amino acids)

Figure 13.3: Phosphoribosylaminoimidazole carboxylase (162 amino acids)

Figure 13.4: Adenylosuccinate Lyase (456 amino acids)

Figure 13.5: Phosphoribosylaminoimidazolecarboamide

and IMP Cyclohydrolase (2 enzymes in one - 512 amino acids)

next: Calculation of Information

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