1. Isolation and characterization of a 30 kDa protein with antifungal activity from leaves of Engelmannia pinnatifida
Q K Huynh, J R Borgmeyer, C E Smith, L D Bell, D M Shah Biochem J. 1996 Jun 15;316 ( Pt 3)(Pt 3):723-7. doi: 10.1042/bj3160723.
During the course of screening plants for novel antifungal activity, we found that a high-molecular-mass fraction of an extract from leaves of Engelmannia pinnatifida exhibited potent and broad-spectrum antifungal activity. In this study a 30 kDa protein from E. pinnatifida leaves was purified to homogeneity by ammonium sulphate precipitation, gel filtration, Mono-Q and C18 reverse-phase column chromatographies. The purified protein showed potent antifungal activity against various plant pathogens with as little as 50 ng. The N-terminal amino acid sequence of the purified protein was determined as XXTKFDFFTLALQXPAXF, where X indicates an unidentified residue. This sequence showed 35-50% sequence identity with purified style glycoproteins associated with self-incompatibility from wild tomato, tobacco and petunia, a phosphate-starvation-induced ribonuclease from cultured tomato cells and the SIR 63.4 kDa protein from yeast.
2. Isolation and characterization of an antifungal protein from Bacillus licheniformis HS10
Zhixin Wang, Yunpeng Wang, Li Zheng, Xiaona Yang, Hongxia Liu, Jianhua Guo Biochem Biophys Res Commun. 2014 Nov 7;454(1):48-52. doi: 10.1016/j.bbrc.2014.10.031. Epub 2014 Oct 14.
Bacillus licheniformis HS10 is a good biocontrol agent against Pseudoperonospora cubensis which caused cucumber downy disease. To identify and characterize the antifungal proteins produced by B.licheniformis HS10, the proteins from HS10 were isolated by using 30-60% ammonium sulfate precipitation, and purified with column chromatography on DEAE Sepharose Fast Flow, RESOURCE Q and Sephadex G-75. And the SDS-PAGE and MALDI-TOF/TOF-MS analysis results demonstrated that the antifungal protein was a monomer with molecular weight of about 55 kDa, identified as carboxypeptidase. Our experiments also showed that the antifungal protein from B. licheniformis HS10 had significantly inhibition on eight different kinds of plant pathogenic fungi, and it was stable with good biological activity at as high as 100°C for 30 min and in pH value ranged from 6 to 10. The biological activity was negatively affected by protease K and 10mM metal cations except Ca(2+).
3. Mechanisms of mTORC1 activation by RHEB and inhibition by PRAS40
Haijuan Yang, Xiaolu Jiang, Buren Li, Hyo J Yang, Meredith Miller, Angela Yang, Ankita Dhar, Nikola P Pavletich Nature. 2017 Dec 21;552(7685):368-373. doi: 10.1038/nature25023. Epub 2017 Dec 13.
The mechanistic target of rapamycin complex 1 (mTORC1) controls cell growth and metabolism in response to nutrients, energy levels, and growth factors. It contains the atypical kinase mTOR and the RAPTOR subunit that binds to the Tor signalling sequence (TOS) motif of substrates and regulators. mTORC1 is activated by the small GTPase RHEB (Ras homologue enriched in brain) and inhibited by PRAS40. Here we present the 3.0 ångström cryo-electron microscopy structure of mTORC1 and the 3.4 ångström structure of activated RHEB-mTORC1. RHEB binds to mTOR distally from the kinase active site, yet causes a global conformational change that allosterically realigns active-site residues, accelerating catalysis. Cancer-associated hyperactivating mutations map to structural elements that maintain the inactive state, and we provide biochemical evidence that they mimic RHEB relieving auto-inhibition. We also present crystal structures of RAPTOR-TOS motif complexes that define the determinants of TOS recognition, of an mTOR FKBP12-rapamycin-binding (FRB) domain-substrate complex that establishes a second substrate-recruitment mechanism, and of a truncated mTOR-PRAS40 complex that reveals PRAS40 inhibits both substrate-recruitment sites. These findings help explain how mTORC1 selects its substrates, how its kinase activity is controlled, and how it is activated by cancer-associated mutations.
