Recent estimates suggest that >300 million people are afflicted by serious fungal infections worldwide. Current antifungal drugs are static and toxic and/or have a narrow spectrum of activity. Thus, there is an urgent need for the development of new antifungal drugs. The fungal sphingolipid glucosylceramide (GlcCer) is critical in promoting virulence of a variety of human-pathogenic fungi. In this study, we screened a synthetic drug library for compounds that target the synthesis of fungal, but not mammalian, GlcCer and found two compounds [N′-(3-bromo-4-hydroxybenzylidene)-2-methylbenzohydrazide (BHBM) and its derivative, 3-bromo-N′-(3-bromo-4-hydroxybenzylidene) benzohydrazide (D0)] that were highly effective in vitro and in vivo against several pathogenic fungi. BHBM and D0 were well tolerated in animals and are highly synergistic or additive to current antifungals. BHBM and D0 significantly affected fungal cell morphology and resulted in the accumulation of intracellular vesicles. Deep-sequencing analysis of drug-resistant mutants revealed that four protein products, encoded by genes APL5, COS111, MKK1, and STE2, which are involved in vesicular transport and cell cycle progression, are targeted by BHBM.

The Photosystem II reaction center is vulnerable to photoinhibition. The D1 and D2 proteins, lying at the core of the photosystem, are susceptible to oxidative modification by reactive oxygen species that are formed by the photosystem during illumination. Using spin probes and EPR spectroscopy, we have determined that both O 2 . The identification of specific amino acid residues oxidized by reactive oxygen species provides insights into the mechanism of damage to the D1 and D2 proteins under light stress.photosynthesis | Photosystem II | reactive oxygen species | photo inhibition | mass spectrometry P hotosystem II (PSII) functions as a water-plastoquinone oxidoreductase (1, 2) and is a thylakoid membrane pigmentprotein complex present in all oxygenic photosynthetic organisms (cyanobacteria, algae, and higher plants). Current high-resolution structures of thermophilic cyanobacterial PSII (3, 4), and lower resolution structures of the red algal (5) and higher plant photosystems (6), have been critically important in furthering our understanding of the molecular organization of PSII. Structurally, the PSII reaction center core is composed of five proteins: D1, D2, the α-and β-subunits of cytochrome b 559 , and PsbI. These components bind all of the redox-active cofactors of PSII.Excitation energy transfer and electron transport within PSII are unavoidably associated with production of reactive oxygen species (ROS) when the absorption of light by the chlorophyll antenna exceeds the capacity for energy utilization. Many mechanisms for ROS production have been proposed (for reviews, see refs. 7 and 8). Briefly, singlet oxygen ( 1 O 2 ) may be formed by excitation energy transfer from triplet chlorophylls (formed either by the change in orientation of the spin of an excited electron in the PSII antenna complex, or via charge recombination of the primary radical pair 3 [P 680 •+ Pheo •− ]) to O 2 (9, 10). ROS production by electron transport involves either the two-electron oxidation of water or the one-electron reduction of O 2 on the PSII electron donor and acceptor sides, respectively. On the PSII electron donor side, a twoelectron oxidation of water leads to the formation of hydrogen peroxide (H 2 O 2 ), which may be oxidized to the superoxide anion radical (O 2•−

As a light-driven water-plastoquinone oxidoreductase, Photosystem II produces molecular oxygen as an enzymatic product. Additionally, under a variety of stress conditions, reactive oxygen species are produced at or near the active site for oxygen evolution. In this study, Fourier-transform ion cyclotron resonance mass spectrometry was used to identify oxidized amino acid residues located in several core Photosystem II proteins (D1, D2, CP43 and CP47) isolated from spinach Photosystem II membranes. While the majority of these oxidized residues (81%) are located on the oxygenated solvent-exposed surface of the complex, several residues on the CP43 protein (354E, 355T, 356M and 357R) which are in close proximity (<15 Å) to the Mn4CaO5 active site are also modified. These residues appear to be associated with putative oxygen/reactive oxygen species exit channel(s) in the photosystem. These results are discussed within the context of a number of computational studies which have identified putative oxygen channels within the photosystem.

Prostatic adenocarcinomas depend on androgen for growth and survival. First line treatment of disseminated disease exploits this dependence by specifically targeting androgen receptor function. Clinical evidence has shown that androgen receptor is reactivated in recurrent tumors despite the continuance of androgen deprivation therapy. Several factors have been shown to restore androgen receptor activity under these conditions, including somatic mutation of the androgen receptor ligand-binding domain. We have shown previously that select tumor-derived mutants of the androgen receptor are receptive to activation by bisphenol A (BPA), an endocrine-disrupting compound that is leached from polycarbonate plastics and epoxy resins into the human food supply. Moreover, we have shown that BPA can promote cell cycle progression in cultured prostate cancer cells under conditions of androgen deprivation. Here, we challenged the effect of BPA on the therapeutic response in a xenograft model system of prostate cancer containing the endogenous BPA-responsive AR-T877A mutant protein. We show that after androgen deprivation, BPA enhanced both cellular proliferation rates and tumor growth. These effects were mediated, at least in part, through androgen receptor activity, as prostate-specific antigen levels rose with accelerated kinetics in BPA-exposed animals. Thus, at levels relevant to human exposure, BPA can modulate tumor cell growth and advance biochemical recurrence in tumors expressing the AR-T877A mutation. [Mol Cancer Ther 2006;5(12):3181 -90]

Protein cross-linking and radiolytic footprinting coupled with highresolution mass spectrometry were used to examine the structure of PsbP and PsbQ when they are bound to Photosystem II. In its bound state, the N-terminal 15-amino-acid residue domain of PsbP, which is unresolved in current crystal structures, interacts with domains in the C terminus of the protein. These interactions may serve to stabilize the structure of the N terminus and may facilitate PsbP binding and function. These interactions place strong structural constraints on the organization of PsbP when associated with the Photosystem II complex. Additionally, amino acid residues in the structurally unresolved loop 3A domain of PsbP ( 90 K-107 V), 93 Y and 96 K, are in close proximity (≤11.4 Å) to the N-terminal 1 E residue of PsbQ. These findings are the first, to our knowledge, to identify a putative region of interaction between these two components. Cross-linked domains within PsbQ were also identified, indicating that two PsbQ molecules can interact in higher plants in a manner similar to that observed by Liu et al. [(2014) Proc Natl Acad Sci 111 (12):4638-4643] in cyanobacterial Photosystem II. This interaction is consistent with either intra-Photosystem II dimer or inter-Photosystem II dimer models in higher plants. Finally, OH • produced by synchrotron radiolysis of water was used to oxidatively modify surface residues on PsbP and PsbQ. Domains on the surface of both protein subunits were resistant to modification, indicating that they were shielded from water and appear to define buried regions that are in contact with other Photosystem II components.oxidoreductase that is found in all oxygenic photosynthetic organisms. This membrane protein complex contains at least 20 protein subunits, 17 of which are intrinsic membrane proteins. Higher plants contain three extrinsic proteins associated with the complex-PsbO, PsbP, and PsbQ-whereas cyanobacteria contain PsbO, PsbU, PsbV, and CyanoQ (a homolog of PsbQ). In higher plants the PsbO, PsbP, and PsbQ proteins are required for optimal rates of O 2 evolution under physiological inorganic calcium and chloride concentrations (1, 2).The PsbO protein appears to play a central role in the stabilization of the manganese cluster in all oxygenic photosynthetic organisms (3). In higher plants, PsbO and PsbP are required for photoautotrophic growth, PS II assembly, and the stabilization of PS II supercomplexes (4-9), with PsbP also being required for normal thylakoid assembly (6). Under low-light growth conditions, PsbQ is required for photoautotrophy (10).Although the crystal structure of cyanobacterial PS II has been resolved to 1.9 Å (11), no crystal structures for higher plant PS II have been presented. The structure and interactions of PsbO with the intrinsic subunits have been approximated by analogy to the cyanobacterial photosystem. Although high-resolution crystal structures of isolated spinach PsbP [1.98 Å; Protein Data Bank (PDB) ID code 2VU4] (12) and PsbQ (1.49 Å; PDB ID code 1VYK) are avai...