Lecture 4

Lecture 4 - to the amide nitrogen of asparagine side...

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Mon. 8.10.09 I. Post-Translational Protein Modifications Protein acetylation o Addition of acetyl group (CH3CO) to the amino group of the N-terminus residue. o Plays an important role in controlling the life span of proteins within cells. Hydroxylation o Hydroxyl groups (OH) can be added to lysine or proline. o Proline is the principal residue to be hydroxylated in proteins, which occurs at the delta-C atom, forming hydroxyproline, and essential element of collagen, in turn a necessary element of connective tissue. Glycosylation o Addition of saccharides to membrane and secreted proteins that contain asparagine, serine or threonine. o The majority of proteins synthesized in the rough ER undergo glycosylation. o Glycosylated proteins are normally found on the cell surface embedded within the plasma membrane. o 2 types: N- linked glycosylation:
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Unformatted text preview: to the amide nitrogen of asparagine side chains. O-linked glycosylation: to the hydroxyl oxygen of serine and threonine side chains. More for regulation o Glycosylation serves various functions: Some proteins do not fold correctly unless they are glycosylated first. Polysaccharides linked at the amide of nitrogen of asparagine confers stability of some secreted glycoproteins where unglycosylated proteins are quickly degraded. Cell adhesion. A protein may be anchored to the membrane if it is attached with lipid molecules. II. Regulation of Protein Function Regulation of protein activity by kinase / phosphatase switch. o Phosphorylation changes a proteins charge and generally leades to a conformational changewhich may lead to activation or inactivation of the protein function. o Ooooooo used in the kinase/phosphatase switch....
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This note was uploaded on 07/21/2010 for the course LS LS3 taught by Professor Lin during the Summer '07 term at UCLA.

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