Cells are controlled by the action of molecules upon molecules. Receptor proteins in the outer cell membrane sense the environment and may subsequently induce changes in the states of specific proteins inside the cell. These proteins then interact again and convey the signal further to other proteins and so forth, until some appropriate action is taken. The final results of such signaling may be a transcription regulation, thereby making more of some kinds of proteins. The reader is reminded that proteins are produced from DNA through a two-step process, where first the DNA code is transcribed into mRNA by an RNA polymerase, and subsequently, the mRNA is translated into a protein by a ribosome. This is illustrated in Figure 1. The simplest way that one protein regulates the production rate of another protein is illustrated in Figure 2. The regulated protein may in turn regulate other proteins, and thereby be part of the transcription regulatory network. Regulatory genetic networks are essential for epigenetics and thus multicellular life, but are not essential for life. In fact, there exist prokaryotes with nearly no genetic regulation. (Figure presented) An interesting overall observation dealing with the architecture of genetic regulatory networks is that the fraction of proteins that regulate other proteins Nreg/N increases with total number of proteins N. In other words, the relative size of the bureaucracy increases with system size. In fact for prokaryotes, the fraction of regulators increases linearly with the system size, reaching ~10% for the prokaryote Pseudomonas auriginosa with....
ASJC Scopus subject areas
- General Physics and Astronomy