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Kent N Strodtman, Severin E Stevenson, James K Waters, Thomas P Mawhinney, Jay J Thelen, Joseph C Polacco, David W Emerich
The functional role of the periplasm of nitrogen-fixing bacteroids has not been determined. Proteins were isolated from the periplasm and cytoplasm of Bradyrhizobium diazoefficiens bacteroids and were analyzed using liquid chromatography tandem mass spectrometry proteomics. Identification of bacteroid periplasmic proteins was aided by periplasm prediction programs. Approximately 40% of all the proteins identified as periplasmic in the B. diazoefficiens genome were found expressed in the bacteroid form of the bacteria, indicating the periplasm is a metabolically active symbiotic space...
October 13, 2017: Molecular Plant-microbe Interactions: MPMI
Yufeng Qin, Yaosheng Chen, Zhiguo Liu, Ying Zhang, Hailong Liu, Zuyong He
A mammalian nonclassical secretion sequence derived from mouse Engrailed2 homeoprotein (En2) was used to direct the secretion of the enhanced green fluorescent protein from Pichia pastoris. This signal peptide conferred the transport of enhanced green fluorescent protein into periplasm through an endoplasmic reticulum-golgi independent pathway, without inducing severe unfolded protein response as compared with Saccharomyces cerevisae α-factor preprosequence. This study implies that this mammalian nonclassical signal peptide could be developed as a useful tool for delivering cargoes to the cell surface of yeast...
October 25, 2016: Sheng Wu Gong Cheng Xue Bao, Chinese Journal of Biotechnology
Kathryn M Schultz, Candice S Klug
Lipopolysaccharide (LPS, endotoxin) is the major component of the outer leaflet of the outer membrane of Gram-negative bacteria such as Escherichia coli and Salmonella typhimurium. LPS is a large lipid containing several acyl chains as its hydrophobic base and numerous sugars as its hydrophilic core and O-antigen domains, and is an essential element of the organisms' natural defenses in adverse environmental conditions. LptC is one of seven members of the lipopolysaccharide transport (Lpt) protein family that functions to transport LPS from the inner membrane (IM) to the outer leaflet of the outer membrane of the bacterium...
October 12, 2017: Protein Science: a Publication of the Protein Society
Jyl S Matson, Jonathan Livny, Victor J DiRita
The epidemic pathogen Vibrio cholerae senses and responds to different external stresses it encounters in the aquatic environment and in the human host. One stress that V. cholerae encounters in the host is exposure to antimicrobial peptides on mucosal surfaces. We used massively parallel cDNA sequencing (RNA-Seq) to quantitatively identify the transcriptome of V. cholerae grown in the presence and absence of sub-lethal concentrations of the antimicrobial peptide polymyxin B. We evaluated the transcriptome of both wild type V...
2017: PloS One
Xing-Chi Yu, Chengfeng Yang, Jienv Ding, Xiaogang Niu, Yunfei Hu, Changwen Jin
The bacterial acid-resistant chaperone HdeA is a "conditionally disordered" protein that functions at low pH when it transits from a well-folded dimer to an unfolded monomer. The dimer dissociation and unfolding processes result in exposure of hydrophobic surfaces that allows binding to a broad range of client proteins. To fully elucidate the chaperone mechanism of HdeA, it is crucial to understand how the activated HdeA interacts with its native substrates during acid stress. Herein, we present an NMR study of the pH-dependent HdeA-substrate interactions...
October 10, 2017: Biochemistry
Wooseok Ko, Sanggil Kim, Hyun Soo Lee
Periplasmic binding proteins (PBPs) are members of a widely distributed protein superfamily found in bacteria and archaea, and are involved in the cellular uptake of solutes. In this report, a leucine-binding PBP was engineered to detect l-Leu based on a fluorescence resonance energy transfer (FRET) change upon ligand binding. A fluorescent unnatural amino acid, l-(7-hydroxycoumarin-4-yl)ethylglycine (CouA), was genetically incorporated into the protein as a FRET donor, and a yellow fluorescent protein (YFP) was fused with its N-terminus as a FRET acceptor...
October 10, 2017: Organic & Biomolecular Chemistry
Subramania Kolappan, Karen Y Lo, Chiao Ling Jennifer Shen, Julian A Guttman, Lisa Craig
Francisella tularensis is a potent human pathogen that invades and survives in macrophage and epithelial cells. Two identical proteins, FTT_0924 from F. tularensis subsp. tularensis and FTL_1286 from F. tularensis subsp. holarctica LVS, have previously been identified as playing a role in protection of the bacteria from osmotic shock and its survival in macrophages. FTT_0924 has been shown to localize to the inner membrane, with its C-terminus exposed to the periplasm. Here, crystal structures of the F. novicida homologue FTN_0802, which we call FvfA, in two crystal forms are reported at 1...
October 1, 2017: Acta Crystallographica. Section D, Structural Biology
Derek T A Lamport, Li Tan, Michael Held, Marcia J Kieliszewski
Occam's Razor suggests a new model of pollen tube tip growth based on a novel Hechtian oscillator that integrates a periplasmic arabinogalactan glycoprotein-calcium (AGP-Ca(2+) ) capacitor with tip-localized AGPs as the source of tip-focussed cytosolic Ca(2+) oscillations: Hechtian adhesion between the plasma membrane and the cell wall of the growing tip acts as a piconewton force transducer that couples the internal stress of a rapidly growing wall to the plasma membrane. Such Hechtian transduction opens stretch-activated Ca(2+) channels and activates H(+) -ATPase proton pump efflux that dissociates periplasmic AGP-Ca(2+) resulting in a Ca(2+) influx that activates exocytosis of wall precursors...
October 9, 2017: New Phytologist
Tithi Banerjee, Zeliang Zheng, Jane Abolafia, Shelby Harper, Donald B Oliver
The bacterial Sec-dependent system is the major protein-biogenic pathway for protein secretion across the cytoplasmic membrane or insertion of integral membrane proteins into the phospholipid bilayer. The mechanism of SecA-driven protein transport across the SecYEG channel complex has remained controversial with conflicting claims from biochemical and structural studies regarding the depth and extent of SecA insertion into SecYEG during ongoing protein transport. Here we utilized site-specific in vivo photo-crosslinking to thoroughly map SecY regions that are in contact with SecA during its insertion cycle...
October 6, 2017: Journal of Biological Chemistry
Rachel L Kinsella, Juvenal Lopez, Lauren D Palmer, Nichole D Salinas, Eric P Skaar, Niraj H Tolia, Mario F Feldman
Acinetobacter baumannii, A. nosocomialis, and A. pittii are a frequent cause of multi-drug resistant, healthcare-associated infections. Our previous work demonstrated that A. nosocomialis M2 possesses a functional Type II secretion system (T2SS) that is required for full virulence. Further, we identified the metallo-endopeptidase CpaA, which had been previously shown to cleave human factor V and deregulate blood coagulation, as the most abundant Type II-secreted effector protein. We also demonstrated that its secretion is dependent on CpaB, a membrane-bound chaperone...
October 5, 2017: Journal of Biological Chemistry
H Lotfi, M A Hejazi, M K Heshmati, S A Mohammadi, N Zarghami
Cyanovirin-N (CVN) is well known as an anti-HIV protein. The efficient production of low cost microbicides for preventing the HIV-infection  has lately become a requirement worldwide. The aim of the present study was to optimize the expression of antiviral Cyanovirin-N homology gene found in the indigenous strain of Nostoc ellipsospourum LZN using Response Surface Methodology (RSM) and Protein Structure Analysis. Optimization of three induction factors (IPTG concentration (0.1, 0.55 and 1mM), temperature for bacterial growth (20, 28...
September 30, 2017: Cellular and Molecular Biology
Aline Sampaio, Vanessa Rodrigues Pegos, Elisa Emiko Oshiro, Andrea Balan
In Xanthomonas citri, the bacterium that causes citrus canker, three ATP-binding cassette (ABC) transporters are known to be dedicated to the uptake of sulfur compounds. In this work, using functional, biophysical and structural methods, we showed that NrtT, a periplasmic component of the ABC transporter NrtCB, is an alkanesulfonate-binding protein and that the deletion of the nrtT gene affected xantham gum synthesis, adhesion and biofilm production, similarly to the phenotype obtained in the X. citri ssuA-knockout strain, in which the alkanesulfonate-binding protein SsuA is absent...
October 2017: FEBS Open Bio
Firdaus Samsudin, Alister Boags, Thomas J Piggot, Syma Khalid
Gram-negative bacteria such as Escherichia coli are protected by a complex cell envelope. The development of novel therapeutics against these bacteria necessitates a molecular level understanding of the structure-dynamics-function relationships of the various components of the cell envelope. We use atomistic MD simulations to reveal the details of covalent and noncovalent protein interactions that link the outer membrane to the aqueous periplasmic region. We show that the Braun's lipoprotein tilts and bends, and thereby lifts the cell wall closer to the outer membrane...
October 3, 2017: Biophysical Journal
Yinghong Gu, Yi Zeng, Zhongshan Wang, Changjiang Dong
Outer membrane β-barrel proteins play important roles in importing nutrients, exporting wastes and conducting signals in Gram-negative bacteria, mitochondria and chloroplasts. The outer membrane proteins are inserted and assembled into the outer membrane by OMP85 family proteins. In Escherichia coli , the b-barrel assembly machinery (BAM) contains four lipoproteins BamB, BamC, BamD and BamE, and one outer membrane protein BamA, forming a "top hat"-like structure. Structural and functional studies of the E...
October 3, 2017: Biochemical Journal
Shiwei Zhu, Tatsuro Nishikino, Bo Hu, Seiji Kojima, Michio Homma, Jun Liu
Vibrio species are Gram-negative rod-shaped bacteria that are ubiquitous and often highly motile in aqueous environments. Vibrio swimming motility is driven by a polar flagellum covered with a membranous sheath, but this sheathed flagellum is not well understood at the molecular level because of limited structural information. Here, we use Vibrio alginolyticus as a model system to study the sheathed flagellum in intact cells by combining cryoelectron tomography (cryo-ET) and subtomogram analysis with a genetic approach...
September 25, 2017: Proceedings of the National Academy of Sciences of the United States of America
Lindsey S Marmont, Gregory B Whitfield, Jacquelyn D Rich, Patrick Yip, Laura B Giesbrecht, Carol A Stremick, John C Whitney, Matthew R Parsek, Joe J Harrison, P Lynne Howell
The Pel polysaccharide (PEL) is synthesized by the opportunistic pathogen Pseudomonas aeruginosa and is an important biofilm constituent critical for bacterial virulence and persistence. PEL is a cationic polymer that promotes cell-cell interactions within the biofilm matrix through electrostatic interactions with extracellular DNA (eDNA). Translocation of PEL across the outer membrane is proposed to occur via PelB, a membrane-embedded porin with a large periplasmic domain predicted to contain 19 tetratricopeptide repeats (TPRs)...
September 27, 2017: Journal of Biological Chemistry
Evangelos I Kazakos, Nick Dorrell, Stergios A Polyzos, Georgia Deretzi, Jannis Kountouras
Attaran et al([1]) have recently shown that decreased susceptibility of established Helicobacter pylori (H. pylori) biofilms to specific antibiotics, was associated with the overtly enhanced transcription of two efflux pump genes, hp1165 and hefA, involved in specific resistance to tetracycline and multiple antibiotics, respectively. Apart from antibiotic exposure, secretion of multiple antimicrobial peptides, such as human β-defensins (hβDs), by the gastric epithelium upon Hp challenge, may act as early triggering events that positively impact biofilm formation and thus, antibiotic resistance...
September 7, 2017: World Journal of Gastroenterology: WJG
H Abdizadeh, A R Atilgan, C Atilgan, B Dedeoglu
With the advances in three-dimensional structure determination techniques, high quality structures of the iron transport proteins transferrin and the bacterial ferric binding protein (FbpA) have been deposited in the past decade. These are proteins of relatively large size, and developments in hardware and software have only recently made it possible to study their dynamics using standard computational resources. We review computational techniques towards understanding the equilibrium and kinetic properties of iron transport proteins under different environmental conditions...
October 2, 2017: Metallomics: Integrated Biometal Science
Yasushi Daimon, Chigusa Iwama Masui, Yoshiki Tanaka, Takuya Shiota, Takehiro Suzuki, Ryoji Miyazaki, Hiroto Sakurada, Trevor Lithgow, Naoshi Dohmae, Hiroyuki Mori, Tomoya Tsukazaki, Shin-Ichiro Narita, Yoshinori Akiyama
BepA (formerly YfgC) is an Escherichia coli periplasmic protein consisting of an N-terminal protease domain and a C-terminal tetratricopeptide repeat (TPR) domain. We have previously shown that BepA is a dual functional protein with chaperone-like and proteolytic activities involved in membrane assembly and proteolytic quality control of LptD, a major component of the outer membrane lipopolysaccharide translocon. Intriguingly, BepA can associate with the BAM complex: the β-barrel assembly machinery driving integration of β-barrel proteins into the outer membrane...
September 27, 2017: Molecular Microbiology
Sunil Parthasarathy, Hari Parapatla, Dayananda Siddavattam
Organophosphate hydrolase (OPH) is a membrane-associated lipoprotein. It translocates across the inner membrane via the twin-arginine transport pathway and remains anchored to the periplasmic face of the inner membrane through a diacylglycerol moiety linked to the invariant cysteine residue found at the junction of a SpaseII cleavage site. Due to the existence of a transmembrane helix at the C-terminus of the mature OPH, an inner-membrane topology was predicted suggesting the C-terminus of OPH is cytoplasmic...
October 16, 2017: FEMS Microbiology Letters
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