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Photodynamic protein cross-linking

1981; Elsevier BV; Volume: 647; Issue: 1 Linguagem: Inglês

10.1016/0005-2736(81)90297-2

1879-2642

H. Verweij, T M A R Dubbelman, Johnny Van Steveninck,

Photosynthetic Processes and Mechanisms

Exposure of spectrin to visible light in the presence of a photosensitizer results in photo-oxidation of sensitive amino acid residues and covalent cross-linking of the polypeptides. In a previous paper the cross-linking was ascribed to a secondary reaction between photo-oxidized histidine residues and amino groups. The following observations, described in this paper, are in accordance with this supposition. (1) During illumination of spectrin in the presence of a photosensitizer a pronounced photo-oxidation of histidine residues takes place. (2) Simultaneously a decrease of free amino groups is observed. (3) Semicarbazide protects against cross-linking and is bound to a histidine photo-oxidation product in spectrin. (4) The pH profile of histidine photo-oxidation and subsequent reaction with amino groups is similar to the pH profile of spectrin cross-linking. Amidination of NH2 groups in spectrin does not inhibit cross-linking, as visualized by gel electrophoresis. On the other hand aminidation of denatured myoglobin causes a 50% inhibition of cross-linking. These observations support the notion of NH2-involvement in cross-linking but also demonstrate, that other photodynamic cross-linking mechanisms exist.