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Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix
Abstract. It is thought that the high protein density in the mitochondrial matrix results in severely restricted solute diffusion and metabolite channeling from one enzyme to another without free aqueous-phase diffusion. To test this hypothesis, we measured the diffusion of green fluorescent protein...
Autores principales: | , , , , |
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Formato: | Texto |
Lenguaje: | English |
Publicado: |
The Rockefeller University Press
1998
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2141758/ https://www.ncbi.nlm.nih.gov/pubmed/9472034 |
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author | Partikian, Arthur Ölveczky, Bence Swaminathan, R. Li, Yuxin Verkman, A.S. |
author_facet | Partikian, Arthur Ölveczky, Bence Swaminathan, R. Li, Yuxin Verkman, A.S. |
author_sort | Partikian, Arthur |
collection | PubMed |
description | Abstract. It is thought that the high protein density in the mitochondrial matrix results in severely restricted solute diffusion and metabolite channeling from one enzyme to another without free aqueous-phase diffusion. To test this hypothesis, we measured the diffusion of green fluorescent protein (GFP) expressed in the mitochondrial matrix of fibroblast, liver, skeletal muscle, and epithelial cell lines. Spot photobleaching of GFP with a 100× objective (0.8-μm spot diam) gave half-times for fluorescence recovery of 15–19 ms with >90% of the GFP mobile. As predicted for aqueous-phase diffusion in a confined compartment, fluorescence recovery was slowed or abolished by increased laser spot size or bleach time, and by paraformaldehyde fixation. Quantitative analysis of bleach data using a mathematical model of matrix diffusion gave GFP diffusion coefficients of 2–3 × 10(−7) cm(2)/s, only three to fourfold less than that for GFP diffusion in water. In contrast, little recovery was found for bleaching of GFP in fusion with subunits of the fatty acid β-oxidation multienzyme complex that are normally present in the matrix. Measurement of the rotation of unconjugated GFP by time-resolved anisotropy gave a rotational correlation time of 23.3 ± 1 ns, similar to that of 20 ns for GFP rotation in water. A rapid rotational correlation time of 325 ps was also found for a small fluorescent probe (BCECF, ∼0.5 kD) in the matrix of isolated liver mitochondria. The rapid and unrestricted diffusion of solutes in the mitochondrial matrix suggests that metabolite channeling may not be required to overcome diffusive barriers. We propose that the clustering of matrix enzymes in membrane-associated complexes might serve to establish a relatively uncrowded aqueous space in which solutes can freely diffuse. |
format | Text |
id | pubmed-2141758 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1998 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-21417582008-05-01 Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix Partikian, Arthur Ölveczky, Bence Swaminathan, R. Li, Yuxin Verkman, A.S. J Cell Biol Article Abstract. It is thought that the high protein density in the mitochondrial matrix results in severely restricted solute diffusion and metabolite channeling from one enzyme to another without free aqueous-phase diffusion. To test this hypothesis, we measured the diffusion of green fluorescent protein (GFP) expressed in the mitochondrial matrix of fibroblast, liver, skeletal muscle, and epithelial cell lines. Spot photobleaching of GFP with a 100× objective (0.8-μm spot diam) gave half-times for fluorescence recovery of 15–19 ms with >90% of the GFP mobile. As predicted for aqueous-phase diffusion in a confined compartment, fluorescence recovery was slowed or abolished by increased laser spot size or bleach time, and by paraformaldehyde fixation. Quantitative analysis of bleach data using a mathematical model of matrix diffusion gave GFP diffusion coefficients of 2–3 × 10(−7) cm(2)/s, only three to fourfold less than that for GFP diffusion in water. In contrast, little recovery was found for bleaching of GFP in fusion with subunits of the fatty acid β-oxidation multienzyme complex that are normally present in the matrix. Measurement of the rotation of unconjugated GFP by time-resolved anisotropy gave a rotational correlation time of 23.3 ± 1 ns, similar to that of 20 ns for GFP rotation in water. A rapid rotational correlation time of 325 ps was also found for a small fluorescent probe (BCECF, ∼0.5 kD) in the matrix of isolated liver mitochondria. The rapid and unrestricted diffusion of solutes in the mitochondrial matrix suggests that metabolite channeling may not be required to overcome diffusive barriers. We propose that the clustering of matrix enzymes in membrane-associated complexes might serve to establish a relatively uncrowded aqueous space in which solutes can freely diffuse. The Rockefeller University Press 1998-02-23 /pmc/articles/PMC2141758/ /pubmed/9472034 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
spellingShingle | Article Partikian, Arthur Ölveczky, Bence Swaminathan, R. Li, Yuxin Verkman, A.S. Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix |
title | Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix |
title_full | Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix |
title_fullStr | Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix |
title_full_unstemmed | Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix |
title_short | Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix |
title_sort | rapid diffusion of green fluorescent protein in the mitochondrial matrix |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2141758/ https://www.ncbi.nlm.nih.gov/pubmed/9472034 |
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