豚鼠气单胞菌CB101的GlcNAc利用系统及调控蛋白NagC对chiI转录的调控

Characterization of GlcNAc utilization system and NagC protein regulates transcription of chiI in Aeromonas caviae CB101

L8和L10是豚鼠气单胞菌(Aeromonas caviae)CB101的两株转座子突变株,突变位置发生在nagA基因,可以组成型表达几丁质酶.我们构建了基因文库,利用Southern杂交从中筛选到一个克隆子包含了三个基因:nagB、nagA和nagC.序列分析显示nagBAC的转录方向相同,而且基因的间隔仅有几个碱基.根据已有报道我们推测NagC是几丁质酶的转录调控蛋白,转座子插入nagA破坏了下游的调控蛋白基因nagC的转录和表达,从而几丁质酶成为组成型表达.我们通过构建NagC缺失突变株、凝胶阻滞迁移以及对NagC氨基酸序列的分析初步证明了NagC属于ROK(repressors,opening reading frames,and kinases)家族的调控蛋白,是chiI的转录阻遏因子.

Two of Aeromonas caviae CB101 transposon mutants ,L8 and L10 ,the transposon that insert in nagA gene can secret Chitinase constantly. We screened a clone which contained three genes：nagB, nagA and nagC from genome library of CB101 by Southern blotting. Sequence analysis showed that nagBAC had the same transcription direction and there were a few base pairs in each gap of these three genes. We presumed that NagC was the regulator of Chitinase and the insertion of transposon in nagA broke the transcription of nagC,so that Chitinase of CB101 could express constantly. We constructed nagC deletion mutant for chitinase assay, performed gel shift assay and analyzed amino acid sequence of NagC protein. Finally we proved that NagC belonged to ROK family protein and it acted as regulator of chil primarily.