title: Solute diffusion is hindered in the mitochondrial matrix.
abstract: Intracellular chemical reactions generally constitute reaction-diffusion systems located inside nanostructured compartments like the cytosol, nucleus, endoplasmic reticulum, Golgi, and mitochondrion. Understanding the properties of such systems requires quantitative information about solute diffusion. Here we present a novel approach that allows determination of the solvent-dependent solute diffusion constant (D(solvent)) inside cell compartments with an experimentally quantifiable nanostructure. In essence, our method consists of the matching of synthetic fluorescence recovery after photobleaching (FRAP) curves, generated by a mathematical model with a realistic nanostructure, and experimental FRAP data. As a proof of principle, we assessed D(solvent) of a monomeric fluorescent protein (AcGFP1) and its tandem fusion (AcGFP1(2)) in the mitochondrial matrix of HEK293 cells. Our results demonstrate that diffusion of both proteins is substantially slowed by barriers in the mitochondrial matrix (cristae), suggesting that cells can control the dynamics of biochemical reactions in this compartment by modifying its nanostructure.
authors.affiliation: Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands.
authors.forename: Cindy E J
authors.initials: CE
authors.lastname: Dieteren
authors.forename: Stan C A M
authors.initials: SC
authors.lastname: Gielen
authors.forename: Leo G J
authors.initials: LG
authors.lastname: Nijtmans
authors.forename: Jan A M
authors.initials: JA
authors.lastname: Smeitink
authors.forename: Herman G
authors.initials: HG
authors.lastname: Swarts
authors.forename: Roland
authors.initials: R
authors.lastname: Brock
authors.forename: Peter H G M
authors.initials: PH
authors.lastname: Willems
authors.forename: Werner J H
authors.initials: WJ
authors.lastname: Koopman
mesh_terms: D002451:Cell Compartmentation; D004058:Diffusion; D036681:Fluorescence Recovery After Photobleaching; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure*; D049329:Nanostructures / Q000648:ultrastructure; D011506:Proteins / Q000378:metabolism*; D012996:Solutions
chemical_list: D011506:Proteins; D012996:Solutions; D049452:Green Fluorescent Proteins