Документ взят из кэша поисковой машины. Адрес оригинального документа : http://kodomo.cmm.msu.ru/~robo_tema/Term2/abstract.txt Дата изменения: Fri Mar 7 15:12:23 2008 Дата индексирования: Tue Oct 2 11:48:28 2012 Кодировка: Поисковые слова: missouri

Krishman HB, Pueppke SG.
Department of Plant Pathology, University of Missouri, Columbia 65211.

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.