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12

Life Continuously Acquires New Information

in Dialogue with the Environment

Abstract

All molecules of a cell are closely related to each other. Only this context-related infor­

mation has real meaning. It conveys the cell’s behavior, which is important and correct

for survival. Print errors are constantly selected away in the population. Database

searches and sequence comparisons unlock this biological meaning (in practice, usu­

ally the function of the compared molecule). This is strongly tied to sequence elements

and a defined structure; random sequences make no biological sense. Even the domains

in an enzyme relate to each other, e.g. in the case of glutathione reductase: For the cata­

lytic domain, there are the matching two cofactor domains (for FAD, NAD), the opti­

mal regulatory domain and also the dimerisation domain, otherwise the enzyme would

not function. Similarly, one checks the consistency of sequence analyses. Everything

must fit together; if contradictions arise, one of the partial analysis results was not yet

correctly classified. Also on the level of protein networks everything relates to each

other, it can be deciphered by network analyses: Central proteins (‘hubs’), signaling

cascades and interfering signals, and modifying input (‘cross-talk’). A fascinating and

illustrative example are the KEGG maps of cancer pathways.

First of all, it is fascinating that the central molecule of life, DNA, does nothing but store

information. Obviously, storing information is an important aspect for living beings.

Information is encoded in genes via the DNA molecule. Then the information is tran­

scribed into RNA, transported out of the cell nucleus, and these are then the building

instructions for proteins with which the cell performs its tasks. Originally, this main direc­

tion of information processing in living cells was called the central dogma of molecular

biology. In the meantime, information processing in the opposite direction is also known,

in particular from RNA to DNA, for example via the enzyme reverse transcriptase (for

© Springer-Verlag GmbH Germany, part of Springer Nature 2023

T. Dandekar, M. Kunz, Bioinformatics,

https://doi.org/10.1007/978-3-662-65036-3_12