0000000000430142
AUTHOR
Sonja Geister
The Folding State of the Lumenal Loop Determines the Thermal Stability of Light-Harvesting Chlorophyll a/b Protein
The major light-harvesting protein of photosystem II (LHCIIb) is the most abundant chlorophyll-binding protein in the thylakoid membrane. It contains three membrane-spanning alpha helices; the first and third one closely interact with each other to form a super helix, and all three helices bind most of the pigment cofactors. The protein loop domains connecting the alpha helices also play an important role in stabilizing the LHCIIb structure. Single amino acid exchanges in either loop were found to be sufficient to significantly destabilize the complex assembled in vitro [Heinemann, B., and Paulsen, H. (1999) Biochemistry 38, 14088-14093. Mick, V., Eggert, K., Heinemann, B., Geister, S., and…
Single amino acids in the lumenal loop domain influence the stability of the major light-harvesting chlorophyll a/b complex.
The major light-harvesting complex of photosystem II (LHCIIb) is one of the most abundant integral membrane proteins. It greatly enhances the efficiency of photosynthesis in green plants by binding a large number of accessory pigments that absorb light energy and conduct it toward the photosynthetic reaction centers. Most of these pigments are associated with the three transmembrane and one amphiphilic alpha helices of the protein. Less is known about the significance of the loop domains connecting the alpha helices for pigment binding. Therefore, we randomly exchanged single amino acids in the lumenal loop domain of the bacterially expressed apoprotein Lhcb1 and then reconstituted the muta…