Diffusion of a membrane protein, Tat subunit Hcf106, is highly restricted within the chloroplast thylakoid network.
The thylakoid membrane forms stacked thylakoids interconnected by 'stromal' lamellae. Little is known about the mobility of proteins within this system. We studied a stromal lamellae protein, Hcf106, by targeting an Hcf106-GFP fusion protein to the thylakoids and photobleaching. We find that even small regions fail to recover Hcf106-GFP fluorescence over periods of up to 3 min after photobleaching. The protein is thus either immobile within the thylakoid membrane, or its diffusion is tightly restricted within distinct regions. Autofluorescence from the photosystem II light-harvesting complex in the granal stacks likewise fails to recover. Integral membrane proteins within both the stromal and granal membranes are therefore highly constrained, possibly forming 'microdomains' that are sharply separated.
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom.
Elina
E
Vladimirou
Michael
M
Li
Cassie P
CP
Aldridge
Lorenzo
L
Frigerio
Markus
M
Kirkilionis
Colin
C
Robinson
D002736:Chloroplasts / Q000378:metabolism*; D036681:Fluorescence Recovery After Photobleaching; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism*; D014026:Nicotiana / Q000166:cytology; D014170:Transformation, Genetic; D003313:Zea mays / Q000378:metabolism
C109236:Hcf106 protein, plant; D008565:Membrane Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins