Pathway · 2 proteins
Envelope assembly and division
Membrane and cell-wall enzymes support expansion and partitioning.
How it works
- Penicillin-binding protein 1A, penicillin-binding protein 2 and an FtsI-family transpeptidase cross-link peptidoglycan using the lipid-linked precursors from the module above, while FtsW/RodA/SpoVE family proteins coordinate those activities with the division machinery.
- Prolipoprotein diacylglyceryl transferase lipidates lipoproteins at the membrane, and an L,D-transpeptidase family protein provides an alternative cross-linking chemistry.
- Assembly is coordinated rather than linear: the same precursors feed elongation and division, and protein and lipid components are handled in parallel. The list states which activities are encoded, not the order in which a growing cell uses them.
Grouped by the atlas’s curated pathway map. The table order is not a proven reaction order.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| Probable peptidoglycan glycosyltransferase FtsW | 2.4.99.28 | [GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)](n)-di-trans,octa-cis-undecaprenyl diphosphate + beta-D-GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)-di-trans,octa-cis-undecaprenyl diphosphate = [GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)](n+1)-di-trans,octa-cis-undecaprenyl diphosphate + di-trans,octa-cis-undecaprenyl diphosphate + H(+) | — | 448 | Step named |
| Peptidase M48 domain-containing protein | — | — | Zn(2+) | 425 | System only |
Also part of this pathway
These proteins are described under another pathway, but also take part here.
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| Phosphatidylglycerol--prolipoprotein diacylglyceryl transferaseHome: Not yet placed in a pathway | 2.5.1.145 | L-cysteinyl-[prolipoprotein] + a 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) = an S-1,2-diacyl-sn-glyceryl-L-cysteinyl-[prolipoprotein] + sn-glycerol 1-phosphate + H(+) | — | 272 | Step named |
| Penicillin binding protein 2Home: Wall synthesis and remodeling | — | — | — | 578 | Step named |
| Penicillin binding protein 2Home: Wall synthesis and remodeling | — | — | — | 595 | Step named |
| L,D-TPase catalytic domain-containing proteinHome: Wall synthesis and remodeling | — | — | — | 397 | System only |
| Penicillin-binding protein 1AHome: Wall synthesis and remodeling | 2.4.99.28; 3.4.16.4 | [GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)](n)-di-trans,octa-cis-undecaprenyl diphosphate + beta-D-GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)-di-trans,octa-cis-undecaprenyl diphosphate = [GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala)](n+1)-di-trans,octa-cis-undecaprenyl diphosphate + di-trans,octa-cis-undecaprenyl diphosphate + H(+) | — | 726 | Step named |
Origins
How could a cell divide its envelope in two before the division machinery existed?
Koonin describes a scenario in which life before cells took place inside networks of mineral compartments, with cells appearing later.
Koonin also writes that no intermediate stages in the origin of cells are known: even the simplest cells have a complex energy-coupling membrane, transport systems, large DNA genomes and complex systems for copying the genome and dividing. He concludes that no uniformitarian explanation exists for the origin of cells.
Division must split the inner membrane, the wall and the outer membrane together, at the right place and time, so that each daughter gets a whole envelope and a whole chromosome.
From the books: Koonin, The Logic of Chance, PDF p. 223.
The wider question for this part of the cell: origins for dividing into two cells.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: Peptidoglycan precursors · Wall synthesis and remodeling · Division scaffold · Division-associated membrane parts · Peptidoglycan biosynthesis · Not yet placed in a pathway