Protein secretion zones during overexpression of amylase within the Gram-positive cell wall

BMC Biology

Research Article

Klaus Liebeton¹  Svenja Fiedler²  Peter L. Graumann²  Manuel Strach²  Felicitas Koch² 

[1] BRAIN Biotech AG, Darmstädter Str. 34-36, 64673, Zwingenberg, Germany;Centre for Synthetic Microbiology (SYNMIKRO) and Fachbereich Chemie, Philipps-Universität Marburg, 35032, Marburg, Germany;

关键词: Protein secretion;    Gram-positive cell wall;    Amylase;    SecA;    Bacterial cell biology;   

DOI  :  10.1186/s12915-023-01684-1

 received in 2022-12-14, accepted in 2023-08-16,  发布年份 2023

来源: Springer

【 摘 要 】

BackgroundWhereas the translocation of proteins across the cell membrane has been thoroughly investigated, it is still unclear how proteins cross the cell wall in Gram-positive bacteria, which are widely used for industrial applications. We have studied the secretion of α-amylase AmyE within two different Bacillus strains, B. subtilis and B. licheniformis.ResultsWe show that a C-terminal fusion of AmyE with the fluorescent reporter mCherry is secreted via discrete patches showing very low dynamics. These are visible at many places within the cell wall for many minutes. Expression from a high copy number plasmid was required to be able to see these structures we term “secretion zones”. Zones corresponded to visualized AmyE activity on the surface of cells, showing that they release active enzymes. They overlapped with SecA signals but did not frequently co-localize with the secretionATPase. Single particle tracking showed higher dynamics of SecA and of SecDF, involved in AmyE secretion, at the cell membrane than AmyE. These experiments suggest that SecA initially translocates AmyE molecules through the cell membrane, and then diffuses to a different translocon. Single molecule tracking of SecA suggests the existence of three distinct diffusive states of SecA, which change during AmyE overexpression, but increased AmyE secretion does not appear to overwhelm the system.ConclusionsBecause secretion zones were only found during the transition to and within the stationary phase, diffusion rather than passive transport based on cell wall growth from inside to outside may release AmyE and, thus, probably secreted proteins in general. Our findings suggest active transport through the cell membrane and slow, passive transition through the cell wall, at least for overexpressed proteins, in bacteria of the genus Bacillus.

【 授权许可】

CC BY   
© BioMed Central Ltd., part of Springer Nature 2023

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