REGULATION OF NITROGENASE-2 IN AZOTOBACTER-VINELANDII BY AMMONIUM, MOLYBDENUM, AND VANADIUM
REGULATION OF NITROGENASE-2 IN AZOTOBACTER-VINELANDII BY AMMONIUM, MOLYBDENUM, AND VANADIUM
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DOI：
10.1128/jb.174.12.3884-3888.1992
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发表时间：
1992-06-01
影响因子：
3.2
通讯作者：
BISHOP, PE
中科院分区：
文献类型：
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作者：
JACOBITZ, S;BISHOP, PE
在不存在钼和存在钒的重氮营养条件下，棕色固氮菌通过使用固氮酶-2将N2还原为NH 4+，固氮酶-2是由vnfH（二固氮酶还原酶-2的基因）和vnfDGK（二固氮酶-2亚基的基因）编码的含V的酶复合物。VnfHorfFd和VnfDGK转录本的积累发生在Mo缺乏的条件下，在V的存在和不存在下;然而，在VnfDGK的情况下，蛋白质产物仅在V的存在下积累。这表明V是翻译VnfDGK转录本所需的。此外，在NH 4+存在下，vnfH-lacZ和vnfD-lacZ转录融合体的表达仅部分受到抑制。与vnfH（1.4和1.0 kb），vnfDG（3.4和1.8 kb），和vnfK（3.4 kb）杂交的转录本中检测到的RNA提取的野生型细胞培养与NH 4+在存在或不存在的V。然而，固氮酶-2亚基未检测到在NH 4+的存在下，固氮酶-2解阻遏的细胞提取物。这些结果表明，这种氮源的行为在转录后水平，以及在转录水平。在Mo（有或没有NH 4+）存在下未检测到vnf转录物。
Under diazotrophic conditions in the absence of molybdenum and in the presence of vanadium, Azotobacter vinelandii reduces N2 to NH4+ by using nitrogenase-2, a V-containing enzyme complex encoded by vnfH (the gene for dinitrogenase reductase-2), and vnfDGK (the genes for dinitrogenase-2 subunits). Accumulation of the vnfHorfFd and vnfDGK transcripts occurred under Mo-deficient conditions in the presence and absence of V; however, in the case of vnfDGK, the protein products only accumulated in the presence of V. This suggests that V is required for translation of the vnfDGK transcripts. In addition, expression of vnfH-lacZ and vnfD-lacZ transcriptional fusions was only partially repressed in the presence of NH4+. Transcripts hybridizing with vnfH (1.4 and 1.0 kb), vnfDG (3.4 and 1.8 kb), and vnfK (3.4 kb) were detected in RNA extracted from wild-type cells cultured with NH4+ in the presence or absence of V. However, nitrogenase-2 subunits were not detected in extracts of cells derepressed for nitrogenase-2 in the presence of NH4+. These results indicate that this nitrogen source acts at the posttranscriptional level as well as at the transcriptional level. vnf transcripts were not detected in the presence of Mo (with or without NH4+).