ABSTRACT
Pseudomonas aeruginosa
PAO1 utilizes agmatine as the sole carbon and nitrogen source via two reactions catalyzed successively by agmatine deiminase (encoded by
aguA
; also called agmatine iminohydrolase) and
N
-carbamoylputrescine amidohydrolase (encoded by
aguB
). The
aguBA
and adjacent
aguR
genes were cloned and characterized. The predicted AguB protein (
M
r
32,759; 292 amino acids) displayed sequence similarity (≤60% identity) to enzymes of the β-alanine synthase/nitrilase family. While the deduced AguA protein (
M
r
41,190; 368 amino acids) showed no significant similarity to any protein of known function, assignment of agmatine deiminase to AguA in this report discovered a new family of carbon-nitrogen hydrolases widely distributed in organisms ranging from bacteria to
Arabidopsis
. The
aguR
gene encoded a putative regulatory protein (
M
r
24,424; 221 amino acids) of the TetR protein family. Measurements of agmatine deiminase and
N
-carbamoylputrescine amidohydrolase activities indicated the induction effect of agmatine and
N
-carbamoylputrescine on expression of the
aguBA
operon. The presence of an inducible promoter for the
aguBA
operon in the
aguR
-
aguB
intergenic region was demonstrated by
lacZ
fusion experiments, and the transcription start of this promoter was localized 99 bp upstream from the initiation codon of
aguB
by S1 nuclease mapping. Experiments with knockout mutants of
aguR
established that expression of the
aguBA
operon became constitutive in the
aguR
background. Interaction of AguR overproduced in
Escherichia coli
with the
aguBA
regulatory region was demonstrated by gel retardation assays, supporting the hypothesis that AguR serves as the negative regulator of the
aguBA
operon, and binding of agmatine and
N
-carbamoylputrescine to AguR would antagonize its repressor function.
摘要
铜绿假单胞菌
PAO1 利用
琼脂糖作为唯一的碳源和氮源,通过
琼脂糖脱
氨酶(由
aguA
编码)和 N
N
-
氨基甲酰四氢苏
氨酸酰胺
水解酶(由
aguB
).其中
aguBA
和相邻的
aguR
基因进行了克隆和鉴定。预测的 AguB 蛋白 (
M
r
32,759; 292
氨基酸)显示出与
β-丙氨酸合成酶/硝化酶家族酶的序列相似性(≤60%)。而推导出的 AguA 蛋白 (
M
r
41,190;368 个
氨基酸)与任何已知功能的蛋白质都没有明显的相似性,但本报告中将
琼脂糖脱
氨酶归入 AguA 发现了一个新的碳氮
水解酶家族,该家族广泛分布于从细菌到拟南芥的各种
生物中。
拟南芥
.该家族的
aguR
基因编码一种假定的调控蛋白
M
r
24,424;221 个
氨基酸)。测量γ-
氨基
嘌呤脱
氨酶和
N
-
氨基甲酰普托雷斯辛酰胺
水解酶活性的测定表明,矢车菊碱和
N
-
氨基甲酰
石蒜碱对
aguBA
操作子的表达。诱导性启动子的存在为
aguBA
操作子的诱导启动子
aguR
-
aguB
基因间区域的
lacZ
融合实验证明,该启动子的转录起点位于
aguB
通过 S1
核酸酶图谱确定了该启动子的转录起点。用
基因敲除突变体
aguR
基因敲除突变体的实验证明
aguBA
操作子的表达在
背景下
背景下成为组成型表达。在大肠杆菌中过量生产的 AguR 与
大肠杆菌
与
aguBA
调控区的相互作用,支持了 AguR 作为大肠杆菌中 aguBA
aguBA
操作子的负调控因子,并与
琼脂糖和
N
-
氨基甲酰普托雷斯辛与 AguR 结合将拮抗其抑制功能。