title: Photonic activation of plasminogen induced by low dose UVB.
abstract: Activation of plasminogen to its active form plasmin is essential for several key mechanisms, including the dissolution of blood clots. Activation occurs naturally via enzymatic proteolysis. We report that activation can be achieved with 280 nm light. A 2.6 fold increase in proteolytic activity was observed after 10 min illumination of human plasminogen. Irradiance levels used are in the same order of magnitude of the UVB solar irradiance. Activation is correlated with light induced disruption of disulphide bridges upon UVB excitation of the aromatic residues and with the formation of photochemical products, e.g. dityrosine and N-formylkynurenine. Most of the protein fold is maintained after 10 min illumination since no major changes are observed in the near-UV CD spectrum. Far-UV CD shows loss of secondary structure after illumination (33.4% signal loss at 206 nm). Thermal unfolding CD studies show that plasminogen retains a native like cooperative transition at ~70 ºC after UV-illumination. We propose that UVB activation of plasminogen occurs upon photo-cleavage of a functional allosteric disulphide bond, Cys737-Cys765, located in the catalytic domain and in van der Waals contact with Trp761 (4.3 Å). Such proximity makes its disruption very likely, which may occur upon electron transfer from excited Trp761. Reduction of Cys737-Cys765 will result in likely conformational changes in the catalytic site. Molecular dynamics simulations reveal that reduction of Cys737-Cys765 in plasminogen leads to an increase of the fluctuations of loop 760-765, the S1-entrance frame located close to the active site. These fluctuations affect the range of solvent exposure of the catalytic triad, particularly of Asp646 and Ser74, which acquire an exposure profile similar to the values in plasmin. The presented photonic mechanism of plasminogen activation has the potential to be used in clinical applications, possibly together with other enzymatic treatments for the elimination of blood clots.
authors: Department of Physics and Nanotechnology, Aalborg University, Aalborg, Denmark.
authors: Manuel
authors: M
authors: Correia
authors: Department of Physics and Nanotechnology, Aalborg University, Aalborg, Denmark.
authors: Torben
authors: T
authors: Snabe
authors: BioPhotonics Group, Department of Nanomedicine, International Iberian Nanotechnology Laboratory (INL), Braga, Portugal; School of Chemistry, Bharathidasan University, Tiruchirappalli, India.
authors: Viruthachalam
authors: V
authors: Thiagarajan
authors: BioPhotonics Group, Department of Nanomedicine, International Iberian Nanotechnology Laboratory (INL), Braga, Portugal; Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; The Institute for Lasers, Photonics and Biophotonics; University at Buffalo, The State University of New York, New York, United States of America.
authors: Steffen Bjørn
authors: SB
authors: Petersen
authors: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
authors: Sara R R
authors: SR
authors: Campos
authors: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
authors: António M
authors: AM
authors: Baptista
authors: BioPhotonics Group, Department of Nanomedicine, International Iberian Nanotechnology Laboratory (INL), Braga, Portugal.
authors: Maria Teresa
authors: MT
authors: Neves-Petersen
mesh_terms: D003553:Cystine / Q000737:chemistry; D004789:Enzyme Activation / Q000528:radiation effects; D006801:Humans; D056004:Molecular Dynamics Simulation; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D010958:Plasminogen / Q000737:chemistry*; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D059748:Proteolysis; D014466:Ultraviolet Rays
chemical_list: D003553:Cystine; D010958:Plasminogen
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