A Light-Dependent Mechanism for Massive Accumulation of Manganese in the Photosynthetic Bacterium Synechocystis sp. PCC 6803
| Autor: | Matthew J. Kidd, Nir Keren, Himadri B. Pakrasi, James E. Penner-Hahn |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Cyanobacteria
Light Photosystem II Photosynthetic Reaction Center Complex Proteins chemistry.chemical_element Manganese Biology Photosynthesis Biochemistry Oxidizing agent Radioisotopes Membrane potential Spectrophotometry Atomic Photosystem II Protein Complex Spectrometry X-Ray Emission biology.organism_classification chemistry Periplasmic Binding Proteins Biophysics ATP-Binding Cassette Transporters Photosynthetic bacteria Energy Metabolism Bacterial outer membrane |
| Zdroj: | Biochemistry. 41:15085-15092 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi026892s |
| Popis: | Manganese is an essential micronutrient for many organisms. Because of its unique role in the water oxidizing activity of photosystem II, manganese is required for photosynthetic growth in plants and cyanobacteria. Here we report on the mechanism of manganese uptake in the cyanobacterium Synechocystis sp. PCC 6803. Cells grown in 9 microM manganese-containing medium accumulate up to 1 x 10(8) manganese atoms/cell, bound to the outer membrane (pool A). This pool could be released by EDTA treatment. Accumulation of manganese in pool A was energized by photosynthetic electron flow. Moreover, collapsing the membrane potential resulted in the immediate release of this manganese pool. The manganese in this pool is mainly Mn(II) in a six-coordinate distorted environment. A distinctly different pool of manganese, pool B ( approximately 1.5 x 10(6) atoms/cell), could not be extracted by EDTA. Transport into pool B was light-independent and could be detected only under limiting manganese concentrations (1 nM). Evidently, manganese uptake in Synechocystis 6803 cells occurs in two steps. First, manganese accumulates in the outer membrane (pool A) in a membrane potential-dependent process. Next, manganese is transported through the inner membrane into pool B. We propose that pool A serves as a store that allows the cells to overcome transient limitations in manganese in the environment. |
| Databáze: | OpenAIRE |
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