期刊
JOURNAL OF BACTERIOLOGY
卷 196, 期 19, 页码 3386-3398出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/JB.01877-14
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资金
- National Science Foundation [DMR-1121288]
- National Institutes of Health [1DP2OD008735-01]
- NSF postdoctoral fellowship [1202622]
- WARF graduate fellowship
- NSF [BIR-9512577]
- NIH [S10 RR13790]
- University of Wisconsin Materials Research Science and Engineering Center [DMR-1121288]
- Searle scholars award
- Direct For Biological Sciences
- Div Of Biological Infrastructure [1202622] Funding Source: National Science Foundation
Cardiolipin (CL) is an anionic phospholipid with a characteristically large curvature and is of growing interest for two primary reasons: (i) it binds to and regulates many peripheral membrane proteins in bacteria and mitochondria, and (ii) it is distributed asymmetrically in rod-shaped cells and is concentrated at the poles and division septum. Despite the growing number of studies of CL, its function in bacteria remains unknown. 10-N-Nonyl acridine orange (NAO) is widely used to image CL in bacteria and mitochondria, as its interaction with CL is reported to produce a characteristic red-shifted fluorescence emission. Using a suite of biophysical techniques, we quantitatively studied the interaction of NAO with anionic phospholipids under physiologically relevant conditions. We found that NAO is promiscuous in its binding and has photophysical properties that are largely insensitive to the structure of diverse anionic phospholipids to which it binds. Being unable to rely solely on NAO to characterize the localization of CL in Escherichia coli cells, we instead used quantitative fluorescence microscopy, mass spectrometry, and mutants deficient in specific classes of anionic phospholipids. We found CL and phosphatidylglycerol (PG) concentrated in the polar regions of E. coli cell membranes; depletion of CL by genetic approaches increased the concentration of PG at the poles. Previous studies suggested that some CL-binding proteins also have a high affinity for PG and display a pattern of cellular localization that is not influenced by depletion of CL. Framed within the context of these previous experiments, our results suggest that PG may play an essential role in bacterial physiology by maintaining the anionic character of polar membranes.
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