The PTB domain of tensin: NMR solution structure and phosphoinositides binding studies

Tensin is a protein confined at those discrete and specialized regions of the plasma membrane, known as focal adhesions. It contains, at the C-terminus, a phosphotyrosine binding (PTB) domain that can interact with the cytoplasmic tail of beta-integrins and is necessary for localization of the protein to cell-matrix adhesions. Here, we present the NMR solution structure of the PTB domain of tensin1. Moreover, through NMR binding studies, we demonstrate that the PTB domain of tensin1 is able to interact with phosphatidylinositol 4, 5-diphosphate (PtIns(4,5)P2) and phosphatidylinositol 4-phosphate (PtIns(4)P), presenting higher affinity for the diphosphorylated inositide. Chemical shift mapping studies reveal a putative PtIns(4,5)P2 binding region that is distinct from the predicted integrin beta-tail recognition site. Heteronuclear NOE experiments, recorded in absence and presence of PtIns(4,5)P2, indicate that the interaction with lipids decreases the flexibility of loop regions, predicted to be important for integrin binding, and thus, proposes a possible correlation between the two distinct binding events. Therefore, our studies suggest that capture of lipids by the PTB domain of tensin1 may play a role for the protein function at focal adhesions.     

NMR studies of a heterotypic Sam-Sam domain association: the interaction between the lipid phosphatase Ship2 and the EphA2 receptor

Sterile alpha motif (Sam) domains are protein interaction modules that are implicated in many biological processes mainly via homo- and heterodimerization. It has been recently reported that the lipid phosphatase Ship2 regulates endocytosis of the EphA2 receptor, a process that has been investigated as a possible route to reduce tumor malignancy. A heterotypic Sam-Sam domain interaction is mediating this process. Here, we report NMR and ITC (isothermal titration calorimetry) studies on the Sam domain of Ship2 revealing its three-dimensional structure and its possible mode of interaction with the Sam domain from the EphA2 receptor. These studies have also resulted in the identification of a minimal peptide region of Ship2 that retains binding affinity for the Sam domain of the EphA2 receptor. Hence, this peptide and the detection of key structural elements important for EphA2 receptor endocytosis provide possible ways for the development of novel small molecule antagonists with potential anticancer activity.     

An Ancient Mediterranean Melting Pot: Investigating the Uniparental Genetic Structure and Population History of Sicily and Southern Italy

Due to their strategic geographic location between three different continents, Sicily and Southern Italy have long represented a major Mediterranean crossroad where different peoples and cultures came together over time. However, its multi-layered history of migration pathways and cultural exchanges, has made the reconstruction of its genetic history and population structure extremely controversial and widely debated. To address this debate, we surveyed the genetic variability of 326 accurately selected individuals from 8 different provinces of Sicily and Southern Italy, through a comprehensive evaluation of both Y-chromosome and mtDNA genomes. The main goal was to investigate the structuring of maternal and paternal genetic pools within Sicily and Southern Italy, and to examine their degrees of interaction with other Mediterranean populations. Our findings show high levels of within-population variability, coupled with the lack of significant genetic sub-structures both within Sicily, as well as between Sicily and Southern Italy. When Sicilian and Southern Italian populations were contextualized within the Euro-Mediterranean genetic space, we observed different historical dynamics for maternal and paternal inheritances. Y-chromosome results highlight a significant genetic differentiation between the North-Western and South-Eastern part of the Mediterranean, the Italian Peninsula occupying an intermediate position therein. In particular, Sicily and Southern Italy reveal a shared paternal genetic background with the Balkan Peninsula and the time estimates of main Y-chromosome lineages signal paternal genetic traces of Neolithic and post-Neolithic migration events. On the contrary, despite showing some correspondence with its paternal counterpart, mtDNA reveals a substantially homogeneous genetic landscape, which may reflect older population events or different demographic dynamics between males and females. Overall, both uniparental genetic structures and TMRCA estimates confirm the role of Sicily and Southern Italy as an ancient Mediterranean melting pot for genes and cultures.     

Metal detoxification and homeostasis in Antarctic Notothenioids. A comparative survey on evolution, expression and functional properties of fish and mammal metallothioneins

Organisms from yeast to mammals contain cysteine-rich, heavy metal binding proteins termed metallothioneins. The putative roles of these proteins are trace metal homeostasis and detoxification of poisonous heavy metals. The highly conserved chemical composition and the structural constraints led to the conclusion that metallothioneins of different origin must display remarkably similar features. The present review aims at surveying the studies carried out on the metallothioneins of Antarctic Notothenioidei, a dominating fish group endowed of a number of striking adaptive characters, including reduced (or absent) hematocrit and presence of antifreeze glycoproteins. Given the unique peculiarities of the Antarctic environment, a comparative study of the features of notothenioid metallothioneins could provide new insights into the role of these proteins in physiology and toxicology. The results summarized here show that the metallothioneins of this fish group display a number of features at the level of evolution, expression pattern, structure and function remarkably different from those of mammal metallothioneins.     

Lipidated peptides via post-synthetic thioalkylation promoted by molecular sieves

A thioalkylation procedure, which uses molecular sieves to promote the reaction, was exploited to provide peptides with useful functional groups (lipidic moieties), naturally occurring on proteins as post-translational modifications. The procedure was further implemented to synthesize tailor-made lipidated peptides, interesting tools to investigate biological processes involving their Ras parent proteins. Moreover, the one-pot preparation of multi-alkylated peptides confirms the versatility and flexibility of the employed methodology.