Purification, partial characterization, and subcellular localization of a 38 kilodalton, calcium-regulated protein of Rhizobium fredii USDA208.
Calcium is essential for the growth of rhizobia and the formation of nitrogen-fixing root-nodules on legumes, but its precise role in these processes remains unknown. We have found that Rhizobium fredii USDA208 accumulates a major 38 kDa protein when grown in media supplemented with 0.3-2 microM Cacl2. We have purified this protein and raised polyclonal antibodies against it. The protein initially is synthesized as a 40 kDa precursor which subsequently undergoes calcium-dependent processing to give rise to the mature polypeptide. Subcellular and immunocytochemical localization studies indicate that the 38 kDa protein accumulates preferentially in the periplasmic space. Its N-terminal sequence, AETIKIGVAGPMTG, shows significant homology to the N-termini of amino acid binding proteins from the periplasm, including leucine-, isoleucine-, and valine-specific binding proteins of Pseudomonas aeruginosa and Escherichia coli and a leucine-specific binding protein of E. coli. The R. fredii protein does not, however, bind [3H]-leucine. The 38 kDa protein is encoded by the bacterial chromosome. It is absent in several rhizobia other than R. fredii, but antigenically related polypeptides are present in Escherichia coli and Erwinia carotovora subsp. carotovora.
Krishman
H B
HB
Department of Plant Pathology, University of Missouri, Columbia 65211.
Pueppke
S G
SG
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011550:Pseudomonas aeruginosa / Q000235:genetics; D012231:Rhizobium / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C488923:LivJ protein, E coli; C028332:leucine-isoleucine-valine binding protein, bacteria; D002118:Calcium