Modification of Immobilized Peptides

Abstract

Cells need to regulate protein activity in order to control processes such as cellular metabolism and growth. This can be achieved by directly modulating protein expression or protein activity. The latter is done by posttranslational protein modifications. In addition to modifications such as acetylation, protein phosphorylation is used in vivo especially to control the activity of cellular factors. Three amino acids (serine, tyrosine and threonine) can reversibly be phosphorylated within a given context. However, not all potential phosphorylation sites are actually phosphorylated in vivo and in vitro. Several distinct pathways that transmit extracellular signals to the nucleus or to the translational machinery use phosphorylation cascades to deliver the signal to the target molecule, thereby ensuring a fast, controlled response of the cell. The S6 kinases and the Raf/MAP pathway are well-established examples of these pathways. Cell-cycle checkpoints are controlled by kinases and regulatory phosphorylations.