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#ParA

3 public questions tagged with this topic.

Microbial Physiology

The bacterial partitioning system consists of:

Bacterial genome partitioning analogous mitosis uses conserved tripartite system. Components include ParA ATPase Walker box, ParB DNA binding protein, centromere like DNA site parS. parS consists of short palindrome repeats 16 base pairs each bound specifically by ParB via helix turn helix domain, ParB CTPase forms focus spreading several kilobases forming partition complex that also loads SMC condensin MukBEF. ParA ATP dimer binds nonspecifically to nucleoid periphery, forming oscillating pattern. Interaction ParB triggers ATP hydrolysis releasing ParA allowing movement. Tripartite ParA ParB

Ref: Livny et al., Mol Microbiol 2007, Bacterial partitioning system ParA ParB parS components.

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Microbial Physiology

In bacterial chromosome segregation, ParA is responsible for:

In tripartite ParABS chromosome segregation ParA role dynamic scaffolding providing motive force. ParA proteins family Walker A ATPase dimerize upon ATP binding forming DNA binding competent form coating bacterial chromosome as cargo independent cloud. Upon ATP hydrolysis to ADP affinity for DNA drops, detachment occurs. ParB parS partition complex stimulates ATPase converting ParA ATP to ADP, so region behind moving complex depleted ParA, while front retains high concentration. Newly synthesized ParA ATP rebinds nucleoid generating gradient that directs chemophoretic movement of ParB parS ori

Ref: Lutkenhaus, Annu Rev Biochem, 2020, ParA filament formation pulling chromosomes apart during segregation.

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Microbial Physiology

What is the primary function of ParA and ParB proteins in bacterial cells?

Stable inheritance of chromosome and low copy plasmids cannot rely on random diffusion given small cell volume, requires active segregation machinery. ParA and ParB constitute conserved partition system. ParB centromere binding protein binds parS sequence palindromic heptad repeats near origin or on plasmid forming large nucleoprotein complex via spreading oligomerization stimulated by CTP binding, also recruits SMC condensin compacting DNA. ParA Walker ATPase dimeric ATP bound associates non specifically with nucleoid DNA forming gradient or filamentous cloud. ParB triggers ParA ATPase releas

Ref: Baxter & Funnell, J Bacteriol, 2014, ParA ParB plasmid and chromosome segregation system.

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