#bacterial proteins

Transgenic Plant -2

TALENs are derived from proteins of:

Transcription activator-like effector nucleases originate from plant pathogenic bacteria Xanthomonas genus comprising Xanthomonas oryzae pv. oryzae causing bacterial blight of rice and Xanthomonas citri causing citrus canker. Pathogen delivers effector proteins via type III secretion apparatus into plant cell cytoplasm mimicking eukaryotic transcription factors: N-terminal type III secretion signal, central repeat domain 12-30 tandem repeats of 33-35 amino acids differing at two positions conferring DNA specificity, C-terminal activation domain and nuclear localization signals. Once in nucleus

Ref: Boch Science 2009 326:1509 TALE Xanthomonas; Bogdanove Curr Opin Microbiol; Moscou Bogdanove 2009.

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Microbial Physiology

Which of the following bacterial proteins is a tubulin homolog?

Cytoskeletal homology across domains revealed by structural biology although sequence similarity low. FtsZ protein essential division highly conserved tubulin homolog. Crystal structures show globular N terminal domain with Rossmann fold GTPase active site containing T1 to T6 loops coordinating GTP plus magnesium, H7 helix central, C terminal domain involved filament contacts. Organization identical to alpha beta tubulin dimer architecture. Both polymerize head to tail forming protofilaments, binding GTP promotes assembly, hydrolysis to GDP promotes disassembly causing dynamic instability. Tub

Ref: Erickson et al., Microbiol Rev 2010, FtsZ tubulin homolog structural and functional homology.

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Microbial Physiology

The ParM-ParR-ParC system in bacteria is responsible for:

Type II partition system ParM ParR ParC extensively studied molecularly via electron microscopy and total internal reflection fluorescence revealing filaments pushing plasmids. parC centromere comprises two clusters five 11 base pair direct repeats separated binding ParR dimers forming helical clamp around DNA. ParR directly interacts with ParM filament ends increasing elongation rate. Filaments grow bipolarly inserting monomers at parC ParR junction producing pushing force separating plasmids by up to cell length. After plasmids reach poles ParM hydrolyzes ATP destabilizing filaments recyclin

Ref: Moller-Jensen et al., EMBO J 2002, ParM-ParR-ParC segregation pushing plasmids - Type II system.

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Microbial Physiology

Which protein plays a role in bacterial plasmid segregation?

Low copy plasmids require faithful segregation to avoid loss during division that would be frequent if distribution random. Actin like protein ParM encoded by many IncE plasmids R1 provides pushing mechanism. ParM ATPase polymerizes into left handed double helical filaments structurally resembling F actin despite low sequence identity, two protofilaments wound. Filaments exhibit dynamic instability both ends grow ATP bound, hydrolysis induces catastrophe. In plasmid context, centromere site parC contains repeat sequences bound by adaptor ParR which forms helical oligomer encircling parC formin

Ref: Garner et al., Science 2007, ParM role in bacterial plasmid segregation - actin homolog.

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