Effects of Visible-Light Irradiation of Protoporphyrin IX on the Self-Assembly of Tubulin Heterodimers.

Abstract

The formation and the effects of laser irradiation of the complex formed by protoporphyrin IX (PPIX) and tubulin was investigated. We have used tubulin as a model protein to investigate whether docked photoactive ligands can affect the structure and function of polypeptides upon exposure to visible light. We observed that laser irradiation in the Soret band prompts bleaching of the PPIX, which is accompanied by a sharp decrease in the intensity and average fluorescence lifetime of the protein (dominated by the four tryptophan residues of the tubulin monomer). The kinetics indicate non-trivial effects and suggest that the photosensitization of the PPIX bound to tubulin prompts structural alterations of the protein. These modifications were also observed through changes in the energy transfer between Trp residues and PPIX. The results suggest that laser irradiation produces localized partial unfolding of tubulin and that the changes prompt modification of the formation of microtubules in vitro. Measurements of singlet oxygen formation were inconclusive in determining whether the changes are prompted by reactive oxygen species or other excited state mechanisms.

• Authors: Alicia Vall-Sagarra, Brady McMicken, Santi Nonell, Lorenzo Brancaleon
• Journal: Chemphyschem : a European journal of chemical physics and physical chemistry (Chemphyschem) Vol. 17 Issue 20 Pg. 3269-3282 (Oct 18 2016) ISSN: 1439-7641 [Electronic] Germany
• PMID: 27490308 (Publication Type: Journal Article)
• Copyright: © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemical References

• Protoporphyrins
• Tubulin
• protoporphyrin IX

Topics

• Dimerization
• Fluorescence
• Light
• Protoporphyrins (chemistry)
• Tubulin (chemical synthesis, chemistry)