{'fraction_non_alphanumeric': 0.028268551236749116, 'fraction_numerical': 0.004240282685512367, 'mean_word_length': 6.224489795918367, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Anti‐mitochondrial flavoprotein autoantibodies of patients with myocarditis and dilated cardiomyopathy (anti‐M7): interaction with flavin‐carrying proteins, effect of vitamin B2 and epitope mapping

Vitamin B2 and flavin cofactors are transported tightly bound to immunoglobulin in human serum. We reasoned that anti‐mitochondrial flavoprotein autoantibodies (αFp‐AB) present in the serum of patients with myocarditis and cardiomyopathy of unknown aetiology may form immunoglobulin aggregates with these serum proteins. However, immunodiffusion and Western blot assays demonstrated that the flavin‐carrying proteins were not recognized by αFp‐AB. Apparently the flavin moiety in the native protein conformation was inaccessible to αFp‐AB. This conclusion was supported by the absence of an immunoreaction between the riboflavin‐binding protein from egg white and αFP‐AB. Intravenous application of vitamin B2 to rabbits immunized with 6‐hydroxy‐ D‐nicotine oxidase, a bacterial protein carrying covalently attached FAD, did not neutralize αFp‐AB which had been raised in the serum of the animals. FAD‐carrying peptides generated from 6‐hydroxy‐ D‐nicotine oxidase by trypsin and chymotrypsin treatment were not recognized by the αFp‐AB, but those generated by endopeptidase Lys were. This demonstrates that the epitope recognized by αFp‐AB comprises, besides the flavin moiety, protein secondary structure elements.