title: Heat-induced unfolding of apo-CP43 studied by fluorescence spectroscopy and CD spectroscopy.
abstract: CP43 is a chlorophyll-binding protein, which acts as a conduit for the excitation energy transfer. The thermal stability of apo-CP43 was studied by intrinsic fluorescence, exogenous ANS fluorescence, and circular dichroism spectroscopy. Under heat treatment, the structure of apo-CP43 changed and existed transition state occurred between 56 and 62 °C by the intrinsic, exogenous ANS fluorescence and the analysis of hydrophobicity. Besides, the isosbestic point of the sigmoidal curve was 58.10 ± 1.02 °C by calculating α-helix transition and the Tm was 56.45 ± 0.52 and 55.59 ± 0.68 °C by calculating the unfolded fraction of tryptophan and tyrosine fluorescence, respectively. During the process of unfolding, the hydrophobic structure of C-terminal segment firstly started to expose at 40 °C, and then the hydrophobic cluster adjacent to the N-terminal segment also gradually exposed to hydrophilic environment with increasing temperature. Our results indicated that heat treatment, especially above 40 °C, has an important impact on the structural stability of apo-CP43.
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
authors.forename: Qing-Jie
authors.initials: QJ
authors.lastname: Xiao
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
authors.forename: Zai-Geng
authors.initials: ZG
authors.lastname: Li
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
authors.forename: Jiao
authors.initials: J
authors.lastname: Yang
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: He
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Xi
authors.affiliation: Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China. dulinfang@scu.edu.cn.
authors.forename: Lin-Fang
authors.initials: LF
authors.lastname: Du
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D004735:Energy Transfer; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005453:Fluorescence; D006358:Hot Temperature; D057927:Hydrophobic and Hydrophilic Interactions; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D013050:Spectrometry, Fluorescence; D014364:Tryptophan
chemical_list: D045332:Photosystem II Protein Complex; C083100:photosystem II, chlorophyll binding protein, CP-43; D002734:Chlorophyll; D014364:Tryptophan
keywords: ANS; Circular dichroism; Fluorescence; Structural rearrangement; Thermal stability; apo-CP43