Towards the development of Bacillus subtilis as a cell factory for membrane proteins and protein complexes

Background: The Gram-positive bacterium Bacillus subtilis is an important producer of high quality industrial enzymes and a few eukaryotic proteins. Most of these proteins are secreted into the growth medium, but successful examples of cytoplasmic protein production are also known. Therefore, one may anticipate that the high protein production potential of B. subtilis can be exploited for protein complexes and membrane proteins to facilitate their functional and structural analysis. The high quality of proteins produced with B. subtilis results from the action of cellular quality control systems that efficiently remove misfolded or incompletely synthesized proteins. Paradoxically, cellular quality control systems also represent bottlenecks for the production of various heterologous proteins at significant concentrations. Conclusion: While inactivation of quality control systems has the potential to improve protein production yields, this could be achieved at the expense of product quality. Mechanisms underlying degradation of secretory proteins are nowadays well understood and often controllable. It will therefore be a major challenge for future research to identify and modulate quality control systems of B. subtilis that limit the production of high quality protein complexes and membrane proteins, and to enhance those systems that facilitate assembly of these proteins.

Towards the development of as a cell factory for membrane proteins and protein complexes-3

Prises a peripheral motor domain SecA, the protein-conducting channel SecYEG, and the accessory proteins SecDF(yajC) and YidC. Membrane proteins are cotranslationally targeted to the Sec translocase as ribosome-bound nascent chains by the SRP and the SRP-receptor FtsY. FtsY associates with the SecY subunit of the Sec translocase, and associates with SRP in a GTP-dependent fashion. GTP hydrolysis at FtsY and SRP effects the release of the ribosome-nascent chain complex from SRP to the SecY subunit of the Sec translocase. Next, chain elongation at the ribosome is directly coupled to the SecY-mediated insertion of the nascent membrane protein into the cytoplasmic membrane. During membrane insertion, newly synthesized transmembrane segments of nascent membrane proteins contact YidC, which may facilitate the lateral release of these hydrophobic segments into the lipid bilayer and/or assist in their folding and assembly. Translocation of large polar extracellular regions through the SecYEG translocation pore is effected by SecA at the expense of ATP. YidC also acts as a Sec-independent membrane protein insertase for a number of small membrane proteins. These proteins are either targeted directly to YidC, or possibly utilize SRP and FtsY for targeting. How SRP discriminates between SecYEG- and YidC-dependent targeting of nascent membrane proteins is unknown. Abbreviation: PMF, proton motive force.<p><b>Copyright information:</b></p><p>Taken from "Towards the development of as a cell factory for membrane proteins and protein complexes"</p><p>http://www.microbialcellfactories.com/content/7/1/10</p><p>Microbial Cell Factories 2008;7():10-10.</p><p>Published online 4 Apr 2008</p><p>PMCID:PMC2323362.</p><p></p

Towards the development of as a cell factory for membrane proteins and protein complexes-2

FtsA and ZipA are recruited next, independently from one another. Once both FtsA and ZipA have localized, the remaining proteins join the ring in the order indicated. Model for assembly of proteins into the septal ring during vegetative growth of . The assembly of late vegetative division proteins (FtsL, DivIB, DivIC and Pbp2B) is not linear and these components appear to assemble in a completely interdependent manner.<p><b>Copyright information:</b></p><p>Taken from "Towards the development of as a cell factory for membrane proteins and protein complexes"</p><p>http://www.microbialcellfactories.com/content/7/1/10</p><p>Microbial Cell Factories 2008;7():10-10.</p><p>Published online 4 Apr 2008</p><p>PMCID:PMC2323362.</p><p></p

Towards the development of as a cell factory for membrane proteins and protein complexes-0

Prises a peripheral motor domain SecA, the protein-conducting channel SecYEG, and the accessory proteins SecDF(yajC) and YidC. Membrane proteins are cotranslationally targeted to the Sec translocase as ribosome-bound nascent chains by the SRP and the SRP-receptor FtsY. FtsY associates with the SecY subunit of the Sec translocase, and associates with SRP in a GTP-dependent fashion. GTP hydrolysis at FtsY and SRP effects the release of the ribosome-nascent chain complex from SRP to the SecY subunit of the Sec translocase. Next, chain elongation at the ribosome is directly coupled to the SecY-mediated insertion of the nascent membrane protein into the cytoplasmic membrane. During membrane insertion, newly synthesized transmembrane segments of nascent membrane proteins contact YidC, which may facilitate the lateral release of these hydrophobic segments into the lipid bilayer and/or assist in their folding and assembly. Translocation of large polar extracellular regions through the SecYEG translocation pore is effected by SecA at the expense of ATP. YidC also acts as a Sec-independent membrane protein insertase for a number of small membrane proteins. These proteins are either targeted directly to YidC, or possibly utilize SRP and FtsY for targeting. How SRP discriminates between SecYEG- and YidC-dependent targeting of nascent membrane proteins is unknown. Abbreviation: PMF, proton motive force.<p><b>Copyright information:</b></p><p>Taken from "Towards the development of as a cell factory for membrane proteins and protein complexes"</p><p>http://www.microbialcellfactories.com/content/7/1/10</p><p>Microbial Cell Factories 2008;7():10-10.</p><p>Published online 4 Apr 2008</p><p>PMCID:PMC2323362.</p><p></p

Towards the development of as a cell factory for membrane proteins and protein complexes-1

The hexameric DivIVA oligomer. Further oligomerization of DivIVA "doggy-bones" leads to two-dimensional network formation. A tentative model for the two-dimensional DivIVA network [100].<p><b>Copyright information:</b></p><p>Taken from "Towards the development of as a cell factory for membrane proteins and protein complexes"</p><p>http://www.microbialcellfactories.com/content/7/1/10</p><p>Microbial Cell Factories 2008;7():10-10.</p><p>Published online 4 Apr 2008</p><p>PMCID:PMC2323362.</p><p></p