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Vol. 169, No. 3 Conservation of Structure and Location of Rhizobium meliloti and
 

Summary: Vol. 169, No. 3
Conservation of Structure and Location of Rhizobium meliloti and
Klebsiella pneumoniae nifB Genes
WILLIAM J. BUIKEMA,'12t JOHN A. KLINGENSMITH,' SARAH L. GIBBONS,2 AND
FREDERICK M. AUSUBELl*
Department of Genetics, Harvard Medical School, and Department of Molecular Biology, Massachusetts General
Hospital, Boston, Massachusetts 02114,' and Department of Cellular and Developmental Biology, Harvard University,
Cambridge, Massachusetts 021382
Received 28 July 1986/Accepted 25 November 1986
Using transposon TnS-mediated mutagenesis, an essential Rhizobium melloti nitrogen fixation (ni) gene was
identified and located directly downstream of the regulatory gene nifA. Maxicell and DNA sequence analysis
demonstrated that the new gene is transcribed in the same direction as nifA and codes for a 54-kilodalton
protein. In KlebsieUa pneumoniae, the nifBQ operon is located directly downstream of a gene which is
structurally and functionally homologous to the R. meliloti nifA gene. The DNA sequences ofthe K. pneumoniae
nijB and nifQ genes (which code for 51- and 20-kilodalton proteins, respectively) were determined. The DNA
sequence ofthe newly identified R. meliloti gene was approximately 50% homologous to the K. pneumoniae niJB
gene. R. meliloti does not contain a gene homologous to nifQ directly downstream of niJB. The R. meliloti nifp
product shares approximately 40% amino acid homology with the K. pneumoniae niJB product, and 10 of the
12 cysteine residues of the R. meliloti nijB product are conserved with 10 of the 17 cysteine residues of the K.
pneumoniae nifB product.

  

Source: Ausubel, Frederick M. - Department of Genetics, Harvard University

 

Collections: Biology and Medicine