1.Structure of the Bacillus anthracis Sortase A Enzyme Bound to Its Sorting Signal: A FLEXIBLE AMINO-TERMINAL APPENDAGE MODULATES SUBSTRATE ACCESS.
Chan AH1, Yi SW2, Terwilliger AL3, Maresso AW3, Jung ME2, Clubb RT4. J Biol Chem. 2015 Oct 16;290(42):25461-74. doi: 10.1074/jbc.M115.670984. Epub 2015 Aug 31.
The endospore forming bacterium Bacillus anthracis causes lethal anthrax disease in humans and animals. The ability of this pathogen to replicate within macrophages is dependent upon the display of bacterial surface proteins attached to the cell wall by the B. anthracis Sortase A ((Ba)SrtA) enzyme. Previously, we discovered that the class A (Ba)SrtA sortase contains a unique N-terminal appendage that wraps around the body of the protein to contact the active site of the enzyme. To gain insight into its function, we determined the NMR structure of (Ba)SrtA bound to a LPXTG sorting signal analog. The structure, combined with dynamics, kinetics, and whole cell protein display data suggest that the N terminus modulates substrate access to the enzyme. We propose that it may increase the efficiency of protein display by reducing the unproductive hydrolytic cleavage of enzyme-protein covalent intermediates that form during the cell wall anchoring reaction.
2.Evaluation of cystatin C activities against HIV.
Vernekar V, Velhal S, Bandivdekar A1. Indian J Med Res. 2015 Apr;141(4):423-30. doi: 10.4103/0971-5916.159282.
BACKGROUND & OBJECTIVES: Several host defense proteins known to possess antimicrobial activities are present on mucosal surfaces and are consequently found in body fluids of vertebrates. Naturally occurring protease inhibitors like cystatins, especially cystatin C (cys C), are abundantly present in human seminal plasma. Although its antiviral activity against herpes simplex virus (HSV) has been demonstrated, the role of this protein against HIV is not well studied. Therefore, the aim of the present study was to evaluate the anti-HIV activities of cys C, which is present innately in the male reproductive tract.
3.Discrete roles of intracellular phospholipases A2 in human neutrophil cytotoxicity.
Mikami S1, Aiboshi J, Kobayashi T, Kojima M, Morishita K, Otomo Y. J Trauma Acute Care Surg. 2015 Aug;79(2):238-46. doi: 10.1097/TA.0000000000000730.
BACKGROUND: The role of calcium-independent phospholipase A2 (iPLA2), a component of the three major PLA2 families, in acute/chronic inflammatory processes remains elusive. Previous investigations have documented iPLA2-mediated respiratory burst of neutrophils (PMNs); however, the causative isoform of iPLA2 is unidentified. We also demonstrated that the iPLA2γ-specific inhibitor attenuates trauma/hemorrhagic shock-induced lung injury. Therefore, iPLA2γ may be implicated in acute inflammation. In addition, arachidonic acid (AA), which is primarily produced by cytosolic PLA2 (cPLA2), is known to display PMN cytotoxicity, although the relationship between AA and the cytotoxic function is still being debated on. We therefore hypothesized that iPLA2γ regulates PMN cytotoxicity via AA-independent signaling pathways. The study aim was to distinguish the role of intracellular phospholipases A2, iPLA2, and cPLA2, in human PMN cytotoxicity and explore the possibility of the presence of signaling molecule(s) other than AA.
4.A Cell-based Fluorescence Resonance Energy Transfer (FRET) Sensor Reveals Inter- and Intragenogroup Variations in Norovirus Protease Activity and Polyprotein Cleavage.
Emmott E1, Sweeney TR1, Goodfellow I2. J Biol Chem. 2015 Nov 13;290(46):27841-53. doi: 10.1074/jbc.M115.688234. Epub 2015 Sep 11.
The viral protease represents a key drug target for the development of antiviral therapeutics. Because many protease inhibitors mimic protease substrates, differences in substrate recognition between proteases may affect their sensitivity to a given inhibitor. Here we use a cell-based FRET sensor to investigate the activity of different norovirus proteases upon cleavage of various norovirus cleavage sites inserted into a linker region separating cyan fluorescent protein and yellow fluorescent protein. Using this system, we demonstrate that differences in substrate processing exist between proteases from human noroviruses (genogroups I (GI) and II) and the commonly used murine norovirus (MNV, genogroup V) model. These altered the cleavage efficiency of specific cleavage sites both within and between genogroups. The differences observed between these proteases may affect sensitivity to protease inhibitors and the suitability of MNV as a model system for testing such molecules against the human norovirus protease.