Thylakoid-bound proteolytic activity against LHC II [light harvesting complex II] apoprotein in bean

Triton X-100 solubilized thylakoids, isolated from Phaseolus vulgaris chloroplasts, degrade endogenous or exogenously added LHC II. The degradation, as monitored by immunodetection of the remaining LHC II after incubation at 37°C, is activated by Mg(++) and inhibited by pCMB, EDTA, PMSF and benzamid...

Full description

Saved in:
Bibliographic Details
Published in:Photosynthesis research 1995-03, Vol.43 (3), p.241-250
Main Authors: Anastassiou, R, Argyroudi-Akoyunoglou, J H
Format: Article
Language:English
Subjects:
cell membranes
fitocroma
membranas celulares
membrane cellulaire
phaseolus vulgaris
phytochrome
proteasas
protease
proteases
proteinas
proteine
proteins
proteolisis
proteolyse
proteolysis
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Triton X-100 solubilized thylakoids, isolated from Phaseolus vulgaris chloroplasts, degrade endogenous or exogenously added LHC II. The degradation, as monitored by immunodetection of the remaining LHC II after incubation at 37°C, is activated by Mg(++) and inhibited by pCMB, EDTA, PMSF and benzamidine; the activity under high light conditions parallels chlorophyll photooxidation. The thylakoid-bound proteolytic activity is under phytochrome control. Etiolated plants pretreated by a white light pulse, and kept in the dark thereafter, show enhanced proteolytic activity, which follows rhythmical oscillations. On the other hand, chloramphenicol pretreatment of etiolated plants, prior to their transfer to continuous light, reduces the proteolytic activity against LHC II. The results suggest that the degradation involves a serine type protease, which depends on SH group(s), coded by the plastid genome; the protease action on LHC II is regulated by Mg(++), phytochrome, the biological clock and chlorophyll accumulation in the thylakoid. The stroma lamellar fraction, separated from French press disrupted chloroplasts, exhibits higher activity towards exogenous LHC II than the grana fraction. The stroma of intact chloroplasts exhibits also high proteolytic activity, which is drastically reduced when the lysis medium is supplemented with cations. This suggests that the protease is bound mainly on stroma lamellae and peripheral granal membranes, its association to the membranes being possibly under cation control.
ISSN:0166-8595
1573-5079
DOI:10.1007/BF00029937