ABSTRACT

Proteins are normally studied in dilute aqueous solution. However, this is not their normal working environment. The inside of a cell is very different from the typical conditions used to study proteins, and it imposes some major constraints on what proteins can do, and how they can do it [2]. In this chapter, we explore the consequences of the protein environment, and the inherent physical limitations on proteins, that have greatly influenced the way in which proteins work. We will see that the physical shape of the cell and of the proteins that fill it have a major effect on association constants and on-rates. And we will see how proteins get round these problems: by using membranes for their associative processes, by being processive, and by having arms of various types that can reach out from the main protein body to stick to binding partners and reel in the protein. In the final part of this chapter, we see how proteins are covalently modified, and how their limited stability against misfolding has both good and bad consequences.