Structural characteristics of extra-membrane domains and guanidine hydrochloride-induced denaturation of photosystem 2 core antenna complexes CP43 and CP47

Abstract

The structural characteristics of the extra-membrane domains and guanidine hydrochloride-induced denaturation of photosystem 2 (PS2) core antenna complexes CP43 and CP47 were investigated using fluorescence emission and circular dichroism (CD) spectra. The extra-membrane domains of CP43 and CP47 possessed a certain degree of secondary and tertiary structure and not a complete random coil conformation. The tertiary structure and the chlorophyll (Chl) a microenvironment of CP47 were more sensitive to guanidine hydrochloride (GuHCl) than that of CP43. Changes in energy transfer from β-carotene to Chl a corresponded well to changes in the tertiary structure while their correlation with changes in the secondary structure was rather poor. Unlike most of water-soluble proteins, both CP43 and CP47 are partly resistant to denaturation induced by guanidine hydrochloride (GuHCl); the denaturation of CP43 or CP47 is not a two-state process. Those features most probably reflect their character as intrinsic membrane proteins.

The guanidine hydrochloride-induced denaturation of CP43 and CP47 studied by terahertz time-domain spectroscopy

“…This further implied that the denatured CP43 and CP47 were in different unfolding states. Our previous study also showed that, after treatment with GuHCl, the secondary and tertiary structure of CP43 and CP47 both changed and the changes between CP43 and CP47 were different [26] . All the above results demonstrated that THz-TDS could be applied to monitoring the denaturation process of photosynthesis membrane proteins.…”

“…This was consistent with the results obtained from the THz spectra. The reason for this might be related to the fact that the apoprotein of CP43 could protect Chl a more effectively than that of CP47, because the apoprotein structure of CP43 was less sensitive to GuHCl than that of CP47 [26] .…”

Absence of far-red emission band in aggregated core antenna complexes

“…Core antenna complexes are different from the peripheral ones in terms of the amount of lipid, number and type of pigments, and membrane structure. In particular, the extramembrane domains of CP43 and CP47 possesses a certain degree of secondary and tertiary structure (not a complete random coil conformation) and it has been found that the changes in energy transfer from b-carotene to Chl a is directly related to the changes in the tertiary structure of protein (63). CP47 protein binds a total of 16 Chl a molecules, whereas CP43 protein binds a total of 13 Chl a molecules.…”

Spectroscopic study of the light-induced changes of the core antenna complex CP43 in photosystem II

“…Core complex extraction was conducted as previously detailed by Ghanotakis et al (1989). CP43 purification was conducted as outlined by Qu et al (2006) and Picorel et al (2011). Samples were diluted to 6 µg(Chl) mL -1 in a 0.05% L-dodecyl maltoside (DM) (Sigma-Aldrich, USA) 20 mmol L -1 Bis-Tris (pH 6.0) solution.…”