Extracellular Identification of a Processed Type II ComR/ComS Pheromone of Streptococcus mutans
Extracellular Identification of a Processed Type II ComR/ComS Pheromone of Streptococcus mutans
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DOI：
10.1128/jb.00624-12
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发表时间：
2012-08-01
影响因子：
3.2
通讯作者：
Petersen, Fernanda C.
中科院分区：
文献类型：
--
作者：
Khan, Rabia;Rukke, Hakon V.;Petersen, Fernanda C.
能力刺激肽（CSP）和sigx诱导肽（XIP）可以诱导变形链球菌的遗传转化能力。对于这两种信息素，原生肽的直接鉴定尚未完成。最近，在一篇附带的论文中（K. Desai， L. Mashburn-Warren， M. J. Federle, and D. a . Morrison， J. Bacteriol. 194:3774-3780, 2012）中观察到细胞外XIP活性，为天然XIP鉴定提供了理想的条件。为了寻找XIP的身份，对培养上清进行过滤，选择小于3 kDa的肽，然后进行C-18提取。在comS缺失突变体的上清液中未检测到的一个肽，通过串联质谱（MS/MS）碎片化鉴定为与comS c端序列GLDWWSL相同。ComS加工不需要Eep，这是一种参与加工或输入细菌小疏水肽的肽酶，因为Eep的缺失对XIP的产生或合成XIP的反应没有抑制作用。我们研究了细胞外CSP是否也产生。CSP活性检测报告试验以及上清液的质谱分析显示，CSP不存在于可检测水平。此外，csp编码基因comC缺失的突变体产生的内源性XIP水平与非缺失突变体相似。结果表明，XIP信息素的产生是一种自然现象，可能发生在缺乏天然CSP信息素活性的情况下，七肽GLDWWSL是ComS的细胞外加工形式，可能是活性XIP信息素。这是直接鉴定ComR/ComS信息素的首次报道。
The competence-stimulating peptide (CSP) and the sigX-inducing peptide (XIP) are known to induce Streptococcus mutans competence for genetic transformation. For both pheromones, direct identification of the native peptides has not been accomplished. The fact that extracellular XIP activity was recently observed in a chemically defined medium devoid of peptides, as mentioned in an accompanying paper (K. Desai, L. Mashburn-Warren, M. J. Federle, and D. A. Morrison, J. Bacteriol. 194:3774-3780, 2012), provided ideal conditions for native XIP identification. To search for the XIP identity, culture supernatants were filtered to select for peptides of less than 3 kDa, followed by C-18 extraction. One peptide, not detected in the supernatant of a comS deletion mutant, was identified by tandem mass spectrometry (MS/MS) fragmentation as identical to the ComS C-terminal sequence GLDWWSL. ComS processing did not require Eep, a peptidase involved in processing or import of bacterial small hydrophobic peptides, since eep deletion had no inhibitory effect on XIP production or on synthetic XIP response. We investigated whether extracellular CSP was also produced. A reporter assay for CSP activity detection, as well as MS analysis of supernatants, revealed that CSP was not present at detectable levels. In addition, a mutant with deletion of the CSP-encoding gene comC produced endogenous XIP levels similar to those of a nondeletion mutant. The results indicate that XIP pheromone production is a natural phenomenon that may occur in the absence of natural CSP pheromone activity and that the heptapeptide GLDWWSL is an extracellular processed form of ComS, possibly the active XIP pheromone. This is the first report of direct identification of a ComR/ComS pheromone.