6533b824fe1ef96bd1280964

RESEARCH PRODUCT

Kinetic Studies of the Assembly of Plant Light Harvesting Complex II

subject

description

Photosynthesis relies on the correct assembly of pigment binding proteins within the thylakoid membrane. Yet, very little is known about the folding of such membrane proteins. The biochemical difficulties connected with these highly hydrophobic proteins are reflected in the low number of crystal structures available for membrane proteins to date. One of the few available, however, is that of LCHII (1). In addition, LHCII is one of only a handful of membrane proteins that can be regenerated in vitro to a native-like conformation (2,3). These two features make it a good candidate for studying its folding and assembly kinetics. Here, a preliminary study on the assembly kinetics of LHCII as a function of concentration of the native lipid, dipalmitoyl-phosphatidyl-glycerol (PG) is presented. PG seems to be essential for trimeiisation of LHCII (5). Treatment of the trimers with phospholipase leads to monomerisation and and release of several pigments, in particular Chi a. PG is not necessary for assembly of LHCII monomers, which can be achieved in octyl-glucopyranoside (OG) micelles (2,3,4). However, in order to reduce the chlorophyll optical density, previous kinetic studies on LHCII required lower protein and pigment concentrations than are optimal for refolding, and thus the yield of formation of functional complexes was only about 50% (4). The aim of this study was to test whether PG would increase the yield of stable complex formation and investigate its effect on the assembly kinetics. LHCII was refolded in mixed PG/OG micelles.