PMID:1989883

Citation	Niki, H, Jaffé, A, Imamura, R, Ogura, T and Hiraga, S (1991) The new gene mukB codes for a 177 kd protein with coiled-coil domains involved in chromosome partitioning of E. coli.EMBO J. 10:183-93
Abstract	An Escherichia coli temperature sensitive mutant which produces spontaneously normal size anucleate cells at low temperature was isolated. The mutant is defective in a previously undescribed gene, named mukB, located at 21 min on the chromosome. The mukB gene codes for a large protein (approximately 180 kd). A 1534 amino acid protein (176,826 daltons) was deduced from the nucleotide sequence of the mukB gene. Computer analysis revealed that the predicted MukB protein has distinct domains: an amino-terminal globular domain containing a nucleotide binding sequence, a central region containing two alpha-helical coiled-coil domains and one globular domain, and a carboxyl-terminal globular domain which is rich in Cys, Arg and Lys. A 180 kd protein detected in wild-type cell extracts by electrophoresis is absent in mukB null mutants. Although the null mutants are not lethal at low temperature, the absence of MukB leads to aberrant chromosome partitioning. At high temperature the mukB null mutants cannot form colonies and many nucleoids are distributed irregularly along elongated cells. We conclude that the MukB protein is required for chromosome partitioning in E. coli.
Links	PubMed
Keywords	Chromosome; Anucleate cells; Chromosome Partitioning;
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Main Points of the Paper

• mukB gene product is required for chromosome positioning from 22C to 42C
• mukB gene product is not essential at lower temperature, but is essential for cell division at higher temperatures
• mukB is mapped to 21 minutes on the chromosome
• mukB is cloned
• Anucleate cell formation is not due to inhibition of DNA replication
• Nucleotide sequence with putative promoter region and RBS is included
• Predicted amino acid sequence are shown with predicted structural motifs,ATP binding sequence is included

Materials and Methods Used

• Temperature shifts
• Fluorescence microscopy
• Plating
• Computer analysis of sequence

Phenotype Annotations

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Species	Taxon ID	Strain	Gene (if known)	OMP	Phenotype	Details	Evidence	Notes
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Increased number of anucleate cells at 22C or 30C	Morphology	nucleoid morphology of cell	Microscopy	Figure 1B
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Increased number of cell pairs at 22C or 30C	Morphology	one anucleate cell with ~1 unit of cell length and one nucleate cell with 1-2 units	Microscopy	Figure 1B, C, D-
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Increased number of cell pairs at 22C or 30C	Morphology	one nucleate cell with 2 copies of chromosomal DNA and one cell having small amounts at the cell pole	Microscopy	Figure 1E, E', F, F'
Escherichia coli W3110	NCBI:316407	GC7528	ΔmukB::kan	Decreased ability to form colonies at high temperature	Growth	CFUs decreased as the temperature was increased.	Plating Assay	Figure 4A- tested on a variety of media
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Increased chromosomal guillotining during cell division at 22C or 30C	Morphology	one nucleate cell with 2 copies of chromosomal DNA and one cell having small amounts at the cell pole	Microscopy	Figure 1E, E', F, F'
Escherichia coli W3110	NCBI:316407	GC7528	ΔmukB::kan	Increased number of anucleate cells at 22C	Morphology	nucleoid morphology of cell	Microscopy	Figure 1G
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Tiny colony formation at 42C	Morphology		Plating Assay	when grown on L broth overnight
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Heterogeneous cell populations at 37C	Morphology	Liquid cultures grown at 37C produce nucleate cells of normal cell size, elongated cells with many nucleoids, and anucleated cells	Microscopy	Figure 1
Escherichia coli W3110	NCBI:316407	GC7528	ΔmukB::kan	Heterogeneous cell populations at 37C	Morphology	Liquid cultures grown at 37C produce nucleate cells of normal cell size, elongated cells with many nucleoids, and anucleated cells	Microscopy	Figure 1H
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Irregular chromosomal distribution within cell at 42C	Morphology		Microscopy	Figure 1
Escherichia coli W3110	NCBI:316407	SH3367	mukB106	Elongated cell length at 42C	Morphology		Microscopy	Figure 1
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References

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