The hglK gene is required for localization of heterocyst-specific glycolipids in the cyanobacterium Anabaena sp. strain PCC 7120.
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.
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Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637, USA.
Buikema
W J
WJ
Haselkorn
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R
D000595:Amino Acid Sequence; D017033:Anabaena / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D002473:Cell Wall / Q000737:chemistry* / Q000648:ultrastructure; D003001:Cloning, Molecular; D018388:Codon, Terminator; D000458:Cyanobacteria / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D006017:Glycolipids / Q000032:analysis*; D008969:Molecular Sequence Data; D009154:Mutation; D012329:RNA, Bacterial / Q000032:analysis; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins; D018388:Codon, Terminator; D004269:DNA, Bacterial; D006017:Glycolipids; C096746:HglK protein, Anabaena; D012329:RNA, Bacterial