Structural Patterns within Tertiary Structure and PTMs

Structural Patterns within Tertiary Structure

Motif/Fold and Domains

Motif or Fold

A common folding pattern involving two or more elements of secondary structure and the connections between them

Domains

Regions of tertiary structure that are independently stable and often have unique functions

Posttranslational Modification of Proteins PTMs

Most proteins are chemically modified after they are synthesized within a cell

Why PTMs

Increases chemical diversity. Enables regulation of protein activity.

Phosphorylation

Addition of a phosphate to Ser Thr or Tyr. Often causes a conformational change regulating protein activity. Catalyzed by kinases and phosphatases.

Glycosylation

Addition of a carbohydrate to Ser Thr (O linked) or Asn (N linked). Common among extracellular and secreted proteins. Catalyzed by glycosyltransferases and glycosidases

Acetylation

Addition of an acetyl group to Lys or protein N termini. Diverse functions including regulation of gene expression. Catalyzed by deacetylases and acetyltransferases

Prenylation

Addition of a prenyl group to Cys. Targets protein to membranes. Catalyzed by farnesyl transferase or geranylgeranyl transferase

Proteolysis

Many protein are cleaved by proteolysis to their active form. The inactive precursors are called proproteins. Irreversible