SpoVID functions as a non-competitive hub that connects the modules for assembly of the inner and outer spore coat layers in Bacillus subtilis.

Filipa Nunes,Catarina Fernandes,Mónica Serrano,Eleonora Marini,Charles P Moran,Patrick Eichenberger,Adriano O Henriques,Carolina Freitas

doi:10.1111/mmi.14116

Filipa Nunes, Catarina Fernandes + Show 6 more

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https://doi.org/10.1111/mmi.14116

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Abstract

SummaryDuring sporulation in Bacillus subtilis, a group of mother cell‐specific proteins guides the assembly of the coat, a multiprotein structure that protects the spore and influences many of its environmental interactions. SafA and CotE behave as party hubs, governing assembly of the inner and outer coat layers. Targeting of coat proteins to the developing spore is followed by encasement. Encasement by SafA and CotE requires E, a region of 11 amino acids in the encasement protein SpoVID, with which CotE interacts directly. Here, we identified two single alanine substitutions in E that prevent binding of SafA, but not of CotE, to SpoVID, and block encasement. The substitutions result in the accumulation of SafA, CotE and their dependent proteins at the mother cell proximal spore pole, phenocopying a spoVID null mutant and suggesting that mislocalized SafA acts as an attractor for the rest of the coat. The requirement for E in SafA binding is bypassed by a peptide with the sequence of E provided in trans. We suggest that E allows binding of SafA to a second region in SpoVID, enabling CotE to interact with E and SpoVID to function as a non‐competitive hub during spore encasement.

Highlights

All organisms face the challenge of assembling large numbers of proteins into functional cellular machines
During sporulation in Bacillus subtilis, a group of mother cell-specific proteins guides the assembly of the coat, a multiprotein structure that protects the spore and influences many of its environmental interactions
The substitutions result in the accumulation of SafA, CotE and their dependent proteins at the mother cell proximal spore pole, phenocopying a spoVID null mutant and suggesting that mislocalized SafA acts as an attractor for the rest of the coat

Summary

Introduction

All organisms face the challenge of assembling large numbers of proteins into functional cellular machines. During endospore development by Bacillus subtilis and related organisms, a multiprotein, multilayered, structure called the coat is assembled around the surface of the developing endospore. This structure is formed by over 80 proteins and plays protective roles, while regulating germination and mediating interactions with the environment (Henriques and Moran, 2007; McKenney et al, 2013; Driks and Eichenberger, 2016; Setlow et al, 2017). Sporulation begins with a polar division that forms a mother cell and a smaller forespore, the future spore (Fig. 1A). The mother cell undergoes autolysis to relase the spore (Fig. 1A)

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