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J. Bacteriol., 11 1995, 6440-6448, Vol 177, No. 22
K Black, WJ Buikema and R Haselkorn
Mutant strain 543 of the cyanobacterium Anabaena sp. strain PCC 7120 was
originally isolated as a Fox- mutant following chemical mutagenesis.
Ultrastructural analysis shows that in nitrogen-replete media the
vegetative cells of the mutant are more cylindrical and have thicker septa
than those of the wild type, while in nitrogen-free media the mutant
heterocysts lack the normal glycolipid layer external to the cell wall.
Although this layer is absent, strain 543 heterocysts nevertheless contain
heterocyst-specific glycolipids, as determined by thin-layer
chromatography. The mutation in strain 543 is in a gene we have named hglK,
encoding a protein of 727 amino acids. The wild-type HglK protein appears
to contain four membrane-spanning regions followed by 36 repeats of a
degenerate pentapeptide sequence, AXLXX. The mutation in strain 543
introduces a termination codon immediately upstream of the pentapeptide
repeat region. A mutant constructed by insertion of an antibiotic
resistance cassette near the beginning of the hglK gene has the same
phenotype as strain 543. We propose that hglK encodes a protein necessary
for the localization of heterocyst glycolipids and that this function
requires the pentapeptide repeats of the HglK protein.
Copyright © 1995, American Society for Microbiology
The hglK gene is required for localization of heterocyst-specific glycolipids in the cyanobacterium Anabaena sp. strain PCC 7120
Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637, USA.
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