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.

中文翻译：

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膜蛋白质组分析揭示了变形链球菌 Ffh、YidC1 和 YidC2 的重叠和独立功能。


利用比较蛋白质组分析来评估源自致龋细菌变形链球菌的膜样品的相似性和差异，包括野生型菌株和缺乏蛋白质易位机制组件的四种突变体，特别是Δffh 、 ΔyidC1 、 ΔyidC2或Δ ffh/yidC1。这项工作的目的是确定所编码的蛋白质单独或彼此协同作用的程度，并确定各个途径的潜在底物。 Ffh 是信号识别颗粒 (SRP) 的主要蛋白质成分，而yidC1和yidC2是编码膜定位伴侣插入酶 YidC/Oxa/Alb 家族成员的双旁系同源物。我们的结果表明，在大多数膜定位底物的插入中，共翻译 SRP 途径与 YidC1 或 YidC2 协同作用，或者不偏向旁系同源物。在一些情况下，单独的 SRP 途径或单独的 YidC 之一似乎是最相关的。这些数据揭示了ffh 、 yidC1或yidC2删除产生不同表型后果的根本原因。我们的数据进一步表明， ΔyidC2背景中存在的许多膜蛋白可能是无功能的， ΔyidC1能够更好地在生理上适应该旁系同源物的丢失， Δffh和ΔyidC2突变体的共同表型特性可能源于对不同蛋白质的影响，并且与核糖体蛋白质的独立结合并不是 YidC2 的主要功能活性。 最后，基因组突变在ΔyidC2背景中积累，与表型回复一致，包括yidC1 内明显的 W138R 抑制突变。