Department of Oral Biology, University of Florida, Gainesville, Florida.
Division of Biosciences College of Dentistry, The Ohio State University, Columbus, Ohio.
Mol Oral Microbiol. 2019 Aug;34(4):131-152. doi: 10.1111/omi.12261. Epub 2019 Jun 7.
A comparative proteomic analysis was utilized to evaluate similarities and differences in membrane samples derived from the cariogenic bacterium Streptococcus mutans, including the wild-type strain and four mutants devoid of protein translocation machinery components, specifically ∆ffh, ∆yidC1, ∆yidC2, or ∆ffh/yidC1. The purpose of this work was to determine the extent to which the encoded proteins operate individually or in concert with one another and to identify the potential substrates of the respective pathways. Ffh is the principal protein component of the signal recognition particle (SRP), while yidC1 and yidC2 are dual paralogs encoding members of the YidC/Oxa/Alb family of membrane-localized chaperone insertases. Our results suggest that the co-translational SRP pathway works in concert with either YidC1 or YidC2 specifically, or with no preference for paralog, in the insertion of most membrane-localized substrates. A few instances were identified in which the SRP pathway alone, or one of the YidCs alone, appeared to be most relevant. These data shed light on underlying reasons for differing phenotypic consequences of ffh, yidC1 or yidC2 deletion. Our data further suggest that many membrane proteins present in a ∆yidC2 background may be non-functional, that ∆yidC1 is better able to adapt physiologically to the loss of this paralog, that shared phenotypic properties of ∆ffh and ∆yidC2 mutants can stem from impacts on different proteins, and that independent binding to ribosomal proteins is not a primary functional activity of YidC2. Lastly, genomic mutations accumulate in a ∆yidC2 background coincident with phenotypic reversion, including an apparent W138R suppressor mutation within yidC1.
采用比较蛋白质组学分析方法，评估了致龋菌变形链球菌的膜样本的相似性和差异，这些样本包括野生型菌株和四个缺乏蛋白质转运机制成分的突变体，具体为 ∆ffh、∆yidC1、∆yidC2 或 ∆ffh/yidC1。本研究的目的是确定编码蛋白各自独立或协同作用的程度，并鉴定各自途径的潜在底物。Ffh 是信号识别颗粒（SRP）的主要蛋白成分，而 yidC1 和 yidC2 是编码膜定位伴侣插入酶 YidC/Oxa/Alb 家族成员的双重同源基因。我们的研究结果表明，共翻译的 SRP 途径与特定的 YidC1 或 YidC2 协同作用，或者与同源基因无偏好性，共同参与大多数膜定位底物的插入。有少数情况下，SRP 途径或一个 YidC 单独作用似乎更为重要。这些数据揭示了 ffh、yidC1 或 yidC2 缺失产生不同表型后果的潜在原因。我们的数据进一步表明，在 ∆yidC2 背景下存在的许多膜蛋白可能是非功能性的，∆yidC1 更能适应该同源基因缺失的生理需求，∆ffh 和 ∆yidC2 突变体的共同表型特征可能源于对不同蛋白的影响，而 YidC2 与核糖体蛋白的独立结合不是其主要功能活动。最后，在 ∆yidC2 背景下，基因组突变与表型回复同时积累，包括 yidC1 内的明显 W138R 抑制突变。
