The structural basis of PTEN regulation by multi-site phosphorylation.

Phosphatase and tensin homolog (PTEN) is a phosphatidylinositol-3,4,5-triphosphate (PIP) phospholipid phosphatase that is commonly mutated or silenced in cancer. PTEN's catalytic activity, cellular membrane localization and stability are orchestrated by a cluster of C-terminal phosphorylation (phospho-C-tail) events on Ser380, Thr382, Thr383 and Ser385, but the molecular details of this multi-faceted regulation have remained uncertain. Here we use a combination of protein semisynthesis, biochemical analysis, NMR, X-ray crystallography and computational simulations on human PTEN and its sea squirt homolog, VSP, to obtain a detailed picture of how the phospho-C-tail forms a belt around the C2 and phosphatase domains of PTEN.

Analysis of Site-Specific Phosphorylation of PTEN by Using Enzyme-Catalyzed Expressed Protein Ligation.

The activity and localization of PTEN, a tumor suppressor lipid phosphatase that converts the phospholipid PIP3 to PIP2, is governed in part by phosphorylation on a cluster of four Ser and Thr residues near the C terminus. Prior enzymatic characterization of the four monophosphorylated (1p) PTENs by using classical expressed protein ligation (EPL) was complicated by the inclusion of a non-native Cys at the ligation junction (aa379), which may alter the properties of the semisynthetic protein. Here, we apply subtiligase-mediated EPL to create wt 1p-PTENs.

The chemical biology of protein hydropersulfides: Studies of a possible protective function of biological hydropersulfide generation.

The recent discovery of significant hydropersulfide (RSSH) levels in mammalian tissues, fluids and cells has led to numerous questions regarding their possible physiological function. Cysteine hydropersulfides have been found in free cysteine, small molecule peptides as well as in proteins. Based on their chemical properties and likely cellular conditions associated with their biosynthesis, it has been proposed that they can serve a protective function.

The chemical biology of hydropersulfides (RSSH): Chemical stability, reactivity and redox roles.

Recent reports indicate the ubiquitous prevalence of hydropersulfides (RSSH) in mammalian systems. The biological utility of these and related species is currently a matter of significant speculation. The function, lifetime and fate of hydropersulfides will be assuredly based on their chemical properties and reactivity.