Transcript Gene Duplication in the Mo-Fe Protein of Nitrogenase

Enzyme catalyzing Nitrogen Fixation in
Bacteria
Root nodules on legumes
Nitrogenase is the enzyme
found in a variety of bacteria,
some of them symbiotic with
plants
• catalyzes the conversion of molecular nitrogen
(N2) from the air into ammonia (NH3).
• It is found in a variety of bacteria, some of them
symbiotic with plants.
Diversity of N-fixing Bacteria
Choosing the sequence to
compare
• Nitrogenase consists of a molybdenum-iron
(MoFe) protein and an iron (Fe) protein.
The MoFe protein contains 2 alpha protein
chains and 2 beta protein chains.
Trials and Errors
• Constructed a phylogenetic tree of the Mo-Fe
protein of nitrogenase from published nucleic acid
data.
• Tried to get a more coherent tree by eliminating
some of the sequences.
• Tree still not revealing.
• Mistake: using nucleotides, switched to amino
acid sequences for the alpha and beta chains.
Amino Acid sequence
• Obtained amino acid sequence of alpha and
beta subunits of MoFe protein from
Azotobacter vinelandii
• Did an alignment on alpha and beta subunits
and found 20.1% identity and , 78% global
alignment, suggesting that alpha and beta
chains are the product of gene duplication.
Crystallographic structure
• Found crystallographic structure for MoFe
protein from A. vinelandii shown on next
slide.
• Structure Explorer - 1M34
Gene Duplication in the Mo-Fe
Protein of Nitrogenase
Figure 54.18 The nitrogen cycle
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants (Layer 3)
Figure 37.10 Root nodules on legumes
Figure 37.10x Nodules
Figure 37.11 Development of a soybean root nodule
Figure 37.13 Molecular biology of root nodule formation
Figure 37.12 Crop rotation and “green manure”
Figure 27.11 One of the most independent organisms on earth: Cyanobacteria
(Anabaena)
Figure 27.11x1 Cyanobacteria: Gloeothece (top left), Nostoc (top right), Calothrix
(bottom left), Fischerella (bottom right)
Figure 27.11x2 A bloom of cyanobacteria
Nutrient Deficiencies:
Agricultural Importance
Nitrogen deficiency
Figure 54.9 Nutrient addition experiments in a Hudson Bay salt marsh
Figure 27.8 Specialized membranes of prokaryotes