scholarly journals Identification and architecture of a putative secretion tube across mycobacterial outer envelope

2021 ◽  
Vol 7 (34) ◽  
pp. eabg5656
Author(s):  
Xiaoying Cai ◽  
Lei Liu ◽  
Chunhong Qiu ◽  
Chongzheng Wen ◽  
Yao He ◽  
...  
Keyword(s):  
Cell Wall ◽  
Protein Secretion ◽  
Mycobacterium Smegmatis ◽  
Culture Medium ◽  
Protein Transport ◽  
Secreted Protein ◽  
Outer Envelope ◽  
Rotationally Symmetric ◽  
Protein Secretion System ◽  
Transport Tube

Tuberculosis-causing mycobacteria have thick cell-wall and capsule layers that are formed from complex structures. Protein secretion across these barriers depends on a specialized protein secretion system, but none has been reported. We show that Mycobacterium tuberculosis Rv3705c and its homologous MSMEG_6251 in Mycobacterium smegmatis are tube-forming proteins in the mycobacterial envelope (TiME). Crystallographic and cryo-EM structures of these two proteins show that both proteins form rotationally symmetric rings. Two layers of TiME rings pack together in a tail-to-tail manner into a ring-shaped complex, which, in turn, stacks together to form tubes. M. smegmatis TiME was detected mainly in the cell wall and capsule. Knocking out the TiME gene markedly decreased the amount of secreted protein in the M. smegmatis culture medium, and expression of this gene in knocked-out strain partially restored the level of secreted protein. Our structure and functional data thus suggest that TiME forms a protein transport tube across the mycobacterial outer envelope.

scholarly journals Secretion of Cryparin, a Fungal Hydrophobin

1999 ◽  
Vol 65 (12) ◽  
pp. 5431-5435 ◽  
Author(s):  
Patricia M. McCabe ◽  
Neal K. Van Alfen
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Submerged Culture ◽  
Secretory Pathway ◽  
Culture Medium ◽  
Secretory Vesicle ◽  
Cryphonectria Parasitica ◽  
Secreted Protein ◽  
Filamentous Ascomycete ◽  
A Cell

ABSTRACT Cryparin is a cell-surface-associated hydrophobin of the filamentous ascomycete Cryphonectria parasitica. This protein contains a signal peptide that directs it to the vesicle-mediated secretory pathway. We detected a glycosylated form of cryparin in a secretory vesicle fraction, but secreted forms of this protein are not glycosylated. This glycosylation occurred in the proprotein region, which is cleaved during maturation by a Kex2-like serine protease, leaving a mature form of cryparin that could be isolated from both the cell wall and culture medium. Pulse-chase labeling experiments showed that cryparin was secreted through the cell wall, without being bound, into the culture medium. The secreted protein then binds to the cell walls ofC. parasitica, where it remains. Binding of cryparin to the cell wall occurred in submerged culture, presumably because of the lectin-like properties unique to this hydrophobin. Thus, the binding of this hydrophobin to the cell wall is different from that of other hydrophobins which are reported to require a hydrophobic-hydrophilic interface for assembly.

scholarly journals Glutamine synthetase encoded by glnA-1 is necessary for cell wall resistance and pathogenicity of Mycobacterium bovis

Microbiology ◽  
2010 ◽  
Vol 156 (12) ◽  
pp. 3669-3677 ◽  
Author(s):  
Harish Chandra ◽  
Seemi Farhat Basir ◽  
Manish Gupta ◽  
Nirupama Banerjee
Keyword(s):  
Cell Wall ◽  
Glutamine Synthetase ◽  
Mycobacterium Bovis ◽  
Mycobacterium Smegmatis ◽  
Cell Walls ◽  
Culture Medium ◽  
Wild Type Strain ◽  
Glutamine Supplementation ◽  
Antitubercular Drugs ◽  
Cell Wall Chemistry

Pathogenic strains of mycobacteria produce copious amounts of glutamine synthetase (GS) in the culture medium. The enzyme activity is linked to synthesis of poly-α-l-glutamine (PLG) in the cell walls. This study describes a glnA-1 mutant of Mycobacterium bovis that produces reduced levels of GS. The mutant was able to grow in enriched 7H9 medium without glutamine supplementation. The glnA-1 strain contained no detectable PLG in the cell walls and showed marked sensitivity to different chemical and physical stresses such as lysozyme, SDS and sonication. The sensitivity of the mutant to two antitubercular drugs, rifampicin and d-cycloserine, was also increased. The glnA-1 strain infected THP-1 cells with reduced efficiency and was also attenuated for growth in macrophages. A Mycobacterium smegmatis strain containing the M. bovis glnA-1 gene survived longer in THP-1 cells than the wild-type strain and also produced cell wall-associated PLG. The M. bovis mutant was not able to replicate in the organs of BALB/c mice and was cleared within 4–6 weeks of infection. Disruption of the glnA-1 gene adversely affected biofilm formation on polystyrene surfaces. The results of this study demonstrate that the absence of glnA-1 not only attenuates the pathogen but also affects cell surface properties by altering the cell wall chemistry of the organism via the synthesis of PLG; this may be a target for drug development.

scholarly journals A Protein Secretion Pathway Critical for Mycobacterium tuberculosis Virulence Is Conserved and Functional in Mycobacterium smegmatis

2005 ◽  
Vol 187 (4) ◽  
pp. 1238-1245 ◽  
Author(s):  
Scott E. Converse ◽  
Jeffery S. Cox
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Protein Secretion ◽  
Mycobacterium Smegmatis ◽  
Gene Knockout ◽  
Growth Conditions ◽  
Critical Determinant ◽  
Secretion Pathway ◽  
Genes Encoding ◽  
Protein Secretion System ◽  
New Gene

ABSTRACT The Snm protein secretion system is a critical determinant of Mycobacterium tuberculosis virulence. However, genes encoding components of this pathway are conserved among all mycobacteria, including the nonpathogenic saprophyte Mycobacterium smegmatis. We show that the Snm system is operational in M. smegmatis and that secretion of its homologous ESAT-6 and CFP-10 substrates is regulated by growth conditions. Importantly, we show that Snm secretion in M. smegmatis requires genes that are homologous to those required for secretion in M. tuberculosis. Using a gene knockout strategy in M. smegmatis, we have also discovered four new gene products that are essential for Snm secretion, including the serine protease mycosin 1. Despite the evolutionary distance between M. smegmatis and M. tuberculosis, the M. smegmatis Snm system can secrete the M. tuberculosis ESAT-6 and CFP-10 proteins, suggesting that substrate recognition is also conserved between the two species. M. smegmatis, therefore, represents a powerful system to study the multicomponent Snm secretory machine and to understand the role of this conserved system in mycobacterial biology.

scholarly journals SagB Glucosaminidase Is a Determinant of Staphylococcus aureus Glycan Chain Length, Antibiotic Susceptibility, and Protein Secretion

2016 ◽  
Vol 198 (7) ◽  
pp. 1123-1136 ◽  
Author(s):  
Yvonne G. Y. Chan ◽  
Matthew B. Frankel ◽  
Dominique Missiakas ◽  
Olaf Schneewind
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Protein Secretion ◽  
Protein Transport ◽  
Capsular Polysaccharide ◽  
Wall Structure ◽  
Content Type ◽  
Sec Pathway ◽  
Lipid Ii ◽  
Cytoplasmic Proteins

ABSTRACTThe envelope ofStaphylococcus aureusis comprised of peptidoglycan and its attached secondary polymers, teichoic acid, capsular polysaccharide, and protein. Peptidoglycan synthesis involves polymerization of lipid II precursors into glycan strands that are cross-linked at wall peptides. It is not clear whether peptidoglycan structure is principally determined during polymerization or whether processive enzymes affect cell wall structure and function, for example, by generating conduits for protein secretion. We show here thatS. aureuslacking SagB, a membrane-associatedN-acetylglucosaminidase, displays growth and cell-morphological defects caused by the exaggerated length of peptidoglycan strands. SagB cleaves polymerized glycan strands to their physiological length and modulates antibiotic resistance in methicillin-resistantS. aureus(MRSA). Deletion ofsagBperturbs protein trafficking into and across the envelope, conferring defects in cell wall anchoring and secretion, as well as aberrant excretion of cytoplasmic proteins.IMPORTANCEStaphylococcus aureusis thought to secrete proteins across the plasma membrane via the Sec pathway; however, protein transport across the cell wall envelope has heretofore not been studied. We report thatS. aureus sagBmutants generate elongated peptidoglycan strands and display defects in protein secretion as well as aberrant excretion of cytoplasmic proteins. These results suggest that the thick peptidoglycan layer of staphylococci presents a barrier for protein secretion and that SagB appears to extend the Sec pathway across the cell wall envelope.

scholarly journals Signal Peptide-Dependent Protein Transport inBacillus subtilis: a Genome-Based Survey of the Secretome

2000 ◽  
Vol 64 (3) ◽  
pp. 515-547 ◽  
Author(s):  
Harold Tjalsma ◽  
Albert Bolhuis ◽  
Jan D. H. Jongbloed ◽  
Sierd Bron ◽  
Jan Maarten van Dijl
Keyword(s):  
Protein Secretion ◽  
Molecular Mechanisms ◽  
Protein Transport ◽  
Transport Systems ◽  
Future Research ◽  
Yeast Saccharomyces Cerevisiae ◽  
Transport Pathways ◽  
Amino Terminal ◽  
Cell Factories ◽  
A Genome

SUMMARY One of the most salient features of Bacillus subtilis and related bacilli is their natural capacity to secrete a variety of proteins into their environment, frequently to high concentrations. This has led to the commercial exploitation of bacilli as major “cell factories” for secreted enzymes. The recent sequencing of the genome of B. subtilis has provided major new impulse for analysis of the molecular mechanisms underlying protein secretion by this organism. Most importantly, the genome sequence has allowed predictions about the composition of the secretome, which includes both the pathways for protein transport and the secreted proteins. The present survey of the secretome describes four distinct pathways for protein export from the cytoplasm and approximately 300 proteins with the potential to be exported. By far the largest number of exported proteins are predicted to follow the major “Sec” pathway for protein secretion. In contrast, the twin-arginine translocation “Tat” pathway, a type IV prepilin-like export pathway for competence development, and ATP-binding cassette transporters can be regarded as “special-purpose” pathways, through which only a few proteins are transported. The properties of distinct classes of amino-terminal signal peptides, directing proteins into the various protein transport pathways, as well as the major components of each pathway are discussed. The predictions and comparisons in this review pinpoint important differences as well as similarities between protein transport systems in B. subtilis and other well-studied organisms, such as Escherichia coli and the yeast Saccharomyces cerevisiae. Thus, they may serve as a lead for future research and applications.

The extracytoplasmic folding factor PrsA is required for protein secretion only in the presence of the cell wall in Bacillus subtilis

Microbiology ◽  
2003 ◽  
Vol 149 (3) ◽  
pp. 569-577 ◽  
Author(s):  
Eva Wahlström ◽  
Marika Vitikainen ◽  
Vesa P. Kontinen ◽  
Matti Sarvas
Keyword(s):  
Cell Wall ◽  
Bacillus Subtilis ◽  
Protein Secretion ◽  
Folding Factor
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