Entry created on 1 July 2019 (Revision 1.0) Annotator: Rita Pancsa
This entry is part of a multi-component system encompassing the following entries: P0A9A6 P0C093
Basic protein information
Accession P0C093
Common name SlmA
Gene SLMA
Organism Escherichia coli
Uniprot name Nucleoid occlusion factor SlmA
Basic LLPS information
Organelle nuclear body; Ftsz-rich droplets at specific chromosomal DNA sites
Type of experimental evidence
Joined entry P0A9A6 P0C093
Protein region(s) mediating LLPS
1
-
198
Only full-length protein studied
Based on the experimental results of the following publication: 30523075
Molecular features viewer
PDB structures
View on PDBe
Extended LLPS information
Functional description
FtsZ is a soluble GTPase, ancestor of eukaryotic tubulin, that serves as a central element of the division ring in most bacteria. FtsZ reversibly forms condensates in the presence of SlmA, a nucleoid occlusion effector of division site selection, in complex with its specific SlmA-binding sites on the chromosome (SBS). These condensates are consistent with crowding-driven phase-separated droplets. The condensates of FtsZ and SlmA are dynamic, allowing the incorporation of additional protein, the rapid evolution of the integrated FtsZ toward filaments in the presence of GTP, and its recruitment back into the liquid droplets upon GTP depletion. FtsZ SlmA SBS condensates, in which FtsZ remains active for polymerization, were also found in cell-like crowded phase-separated systems revealing their preferential partition into one of the phases, and its accumulation at lipid surfaces (PMID:30523075).
Literature supporting the LLPS: 27725777, 30523075
Functional class of membraneless organelle: protective storage/reservoir
Binding partners (at biological protein concentrations)
1) FtsZ (strictly required for LLPS) 2) specific DNA site SBS (not required for LLPS, but promotes it)
Type of RNA(s) required/used for the LLPS at biological protein concentrations
RNA not required.
Molecular interaction types contributing to LLPS
Not known
Determinants of phase separation and droplet properties
1) protein concentration of FtsZ 2) protein concentration of SlmA 3) ionic strength 4) crowding agent concentration
Membrane cluster No
Partner-dependent Yes
RNA-dependent No
PTM required No
Domain-motif interactions Not known
Discrete oligomerization Not known
Regulation and disease
Post-translational modifications affecting LLPS
Position Residue PTM Effect Reference Modifying enzyme Notes
Isoforms known to affect LLPS
Isoform Effect Reference
All known isoforms containing sequence changes in the LLPS region(s)
Position type Isoform names from UniProt
Disease mutations affecting LLPS
Mutation dbSNP Disease OMIM Effect Reference Notes
Experimental information
Experimental techniques applied to prove/investigate LLPS
Liquid droplets were observed in vitro (particle size and count) in solutions containing FtsZ labeled with Alexa 647 (FtsZ-Alexa 647) (fluorescent tagging), unlabeled SlmA, and fluorescein-labeled 24-bp oligonucleotide with the consensus sequence SBS (SBS-Fl), in which the two dyes colocalized, independently of the macromolecule used to crowd the solution (Ficoll, PEG or dextran), as revealed by confocal microscopy imaging. These findings were confirmed by turbidity experiment (change in optical properties). Change in protein concentration, change in salt concentration, change in the concentration of a crowding agent affected the formation of condensates (particle size and count by microscopy and change in optical properties). The round structures formed by FtsZ-SlmA-SBS were dynamic, a characteristic feature of liquid-like droplets, as revealed by protein capture experiment. Addition of GTP on preformed FtsZ-SlmA-SBS condensates induced the formation of FtsZ fibers in which significant colocalization between FtsZ-Alexa 488 and SBS-Alexa 647 was observed by microscopy. Compared with control samples lacking SlmA-SBS, the fibers were thinner and their lifetime was appreciably shorter, as previously observed in dilute solution. Initially, the fibers coexisted with the round condensates (co-localization), and then, the amount of fibers increased at the expense of the condensates. In open, phase-separated PEG/DNA systems, abundant FtsZ-SlmA-SBS condensates were found, mostly distributed in the DNA phase (co-localization), probably because of the preferential partition of the individual components (FtsZ, SlmA, and the SBS) into this phase. (PMID:30523075).
Experimental observations supporting the liquid material state of the condensate
morphological traits (PMID:30523075) reversibility (PMID:30523075)