Search results for " Quaternary."

Chicken Avidin-related Protein 4/5 Shows Superior Thermal Stability when Compared with Avidin while Retaining High Affinity to Biotin

2003

The protein chicken avidin is a commonly used tool in various applications. The avidin gene belongs to a gene family that also includes seven other members known as the avidin-related genes (AVR). We report here on the extremely high thermal stability and functional characteristics of avidin-related protein AVR4/5, a member of the avidin protein family. The thermal stability characteristics of AVR4/5 were examined using a differential scanning calorimeter, microparticle analysis, and a microplate assay. Its biotin-binding properties were studied using an isothermal calorimeter and IAsys optical biosensor. According to these analyses, in the absence of biotin AVR4/5 is clearly more stable (T…

Structural and Functional Basis for Understanding the Biological Significance of P2X7 Receptor

2020

The P2X7 receptor (P2X7R) possesses a unique structure associated to an as yet not fully understood mechanism of action that facilitates cell permeability to large ionic molecules through the receptor itself and/or nearby membrane proteins. High extracellular adenosine triphosphate (ATP) levels—inexistent in physiological conditions—are required for the receptor to be triggered and contribute to its role in cell damage signaling. The inconsistent data on its activation pathways and the few studies performed in natively expressed human P2X7R have led us to review the structure, activation pathways, and specific cellular location of P2X7R in order to analyze its biological relevance. The ATP-…

Comparative 11A structure of two molluscan hemocyanins from 3D cryo-electron microscopy

2006

Abstract Hemocyanins are giant extracellular proteins that transport oxygen in the hemolymph of many molluscs. Molluscan hemocyanins are cylindrical decamers or didecamers of a 350–400 kDa subunit that contains seven or eight different covalently linked globular functional units (FUs), arranged in a linear manner. Each FU carries a single copper active site and reversibly binds one dioxygen molecule. As a consequence, the decamer can carry up to 70 or 80 O 2 molecules. Although complete sequence information is now available from several molluscan hemocyanins, many details of the quaternary structure are still unclear, including the topology of the 10 subunits within the decamer. Here we sho…

Molecular and topological membrane folding determinants of transient receptor potential vanilloid 2 channel.

2015

Transient Receptor Potential (TRP) channels are related to adaptation to the environment and somatosensation. The transient receptor potential vanilloid (TRPV) subfamily includes six closely evolutionary related ion channels sharing the same domain organization and tetrameric arrangement in the membrane. In this study we have characterized biochemically TRPV2 channel membrane protein folding and transmembrane (TM) architecture. Deleting the first N-terminal 74 residues preceding the ankyrin repeat domain (ARD) show a key role for this region in targeting the protein to the membrane. We have demonstrated the co-translational insertion of the membrane-embedded region of the TRPV2 and its disp…

Structure of the human filamin A actin-binding domain.

2009

Filamin A (FLNa) is a large dimeric protein that binds to actin filaments via its actin-binding domain (ABD). The crystal structure of this domain was solved at 3.2 A resolution. The domain adopts a closed conformation typical of other ABDs, but also forms a dimer both in crystallization conditions and in solution. The structure shows the localization of the residues mutated in patients with periventricular nodular heterotopia or otopalatodigital syndrome. Structural analysis predicts that mutations in both types of disorder may affect actin binding.

Subunit organization of the abalone Haliotis tuberculata hemocyanin type 2 (HtH2), and the cDNA sequence encoding its functional units d, e, f, g and…

1999

We have developed a HPLC procedure to isolate the two different hemocyanin types (HtH1 and HtH2) of the European abalone Haliotis tuberculata. On the basis of limited proteolytic cleavage, two-dimensional immunoelectrophoresis, PAGE, N-terminal protein sequencing and cDNA sequencing, we have identified eight different 40-60-kDa functional units (FUs) in HtH2, termed HtH2-a to HtH2-h, and determined their linear arrangement within the elongated 400-kDa subunit. From a Haliotis cDNA library, we have isolated and sequenced a cDNA clone which encodes the five C-terminal FUs d, e, f, g and h of HtH2. As shown by multiple sequence alignments, defg of HtH2 correspond structurally to defg from Octo…

9 Å cryo-EM structure and molecular model of a gastropod hemocyanin didecamer (KLH1) reveals the architecture of the asymmetric collar

2008

Hemocyanins are blue copper proteins that transport oxygen in the hemolymph of many arthropods and molluscs. Molluscan hemocyanins are decamers, didecamers or multidecamers of a 350–400 kDa polypeptide subunit that is subdivided into seven or eight different functional units (FUs, each with a single copper active site). The quaternary structure is a semi-hollow cylinder consisting of a wall and a collar. Recently, we published a 9 A cryo-EM structure and molecular model of a cephalopod hemocyanin decamer (NpH, from Nautilus pompilius) that answered many hitherto unsolved questions concerning the quaternary structure of molluscan hemocyanin. Notably, it revealed the twisted pathway of the 10…

Is There a Role for Tertiary (TCR) and Quaternary (QCR) Cytoreduction in Recurrent Ovarian Cancer?

2015

BACKGROUND: The aim of the present study was to evaluate the efficacy of tertiary and quaternary cytoreduction in recurrent ovarian cancer patients. PATIENTS AND METHODS:Between January 1997 and December 2014, 53 patients were submitted to cytoreductive surgery for second and third ovarian cancer recurrence at our Unit. RESULTS:Median age at first diagnosis was 48 years (range=20-69). Forty-six patients (86.8%) underwent tertiary cytoreduction. At the time of surgery, isolated and diffuse disease was observed in 48 (90.6%) and 5 (9.4%) patients, respectively. Complete and optimal cytoreduction was obtained in 41 (77.5%) and in 1 (1.9%) patients, respectively. We did not observe any statisti…

Modification of the proteolytic fragmentation pattern upon oxidation of cysteines from ribulose 1,5-bisphosphate carboxylase/oxygenase.

2003

The proteolytic susceptibility of the native CO 2 -fixing photosynthetic enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39, Rubisco) has been shown to increase in vitro after oxidative treatments that affect cysteine thiols. A limited incubation of oxidized (pretreated with the disulfide cystamine) Rubisco from Chlamydomonas reinhardtii with subtilisin or proteinase K generated fragments of molecular mass about 53 kDa (band I in SDS-PAGE) and 47 kDa (band II) derived from the large subunit (55 kDa) of the enzyme. In contrast, proteolysis of the reduced Rubisco (pretreated with the free thiol cysteamine) produced only the 53 kDa band. The same fragmentation pattern was repr…

Paleoecological insight into the straight-tusked elephant population from the late Middle Pleistocene site of Poggetti Vecchi

Il progetto di ricerca s’incentra sullo studio della macrofauna rinvenuta nel sito paleontologico e archeologico di Poggetti Vecchi, scoperto nella località di Roselle situata in provincia di Grosseto. Nello specifico esso è stato focalizzato sulla ricostruzione paleoambientale e paleoecologica dell’area. L’analisi paleobiologica e tafonomica dei resti faunistici è stata perciò inserita all’interno di un progetto multidisciplinare e l’integrazione di tutti i dati paleontologici (relativi a vertebrati, invertebrati, macroresti vegetali e pollini) con quelli stratigrafici ha permesso di ricostruire dettagliatamente l’evoluzione paleoambientale. Nella seconda parte, lo studio paleoecologico è …