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Genetic analysis and cellular localization of the Rhizobium host specificity-determining NodE protein
H P Spaink1, J Weinman, M A Djordjevic
1Department of Plant Molecular Biology, Leiden University, The Netherlands.
The EMBO Journal
|October 1, 1989
Summary
The NodE protein in Rhizobium trifolii and Rhizobium leguminosarum determines distinct host ranges for nodulation. A central 185-amino acid region with minor differences is key to this host specificity.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The nodE gene is crucial for symbiotic interactions between Rhizobium bacteria and legumes.
- Understanding NodE protein function is key to deciphering host specificity in nitrogen fixation.
Purpose of the Study:
- To determine the nucleotide sequence and functional role of the nodE gene in Rhizobium trifolii ANU843.
- To elucidate the structural and functional differences between NodE proteins of R. trifolii and R. leguminosarum.
Main Methods:
- Nucleotide sequencing of the nodE gene.
- Protein homology analysis and prediction of secondary structures.
- Immunological localization of NodE proteins using antibodies.
- Construction and analysis of hybrid nodE genes.
Main Results:
- The nodE gene of R. trifolii ANU843 encodes a 42.0 kDa protein with 78% homology to R. leguminosarum NodE.
- NodE proteins are localized in the cytoplasmic membrane and predicted to have transbilayer alpha-helices.
- The NodE product was identified as the primary determinant of host range specificity between R. trifolii and R. leguminosarum.
- A central 185-amino acid region of NodE, with only 44 non-identical amino acids, dictates host-specific characteristics.
Conclusions:
- The NodE protein plays a critical role in determining the host range of Rhizobium nodulation.
- Specific amino acid variations within a central region of NodE are responsible for differential host recognition.