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Publication Abstract from PubMed

The structure and function of heme proteins are regulated by diverse post-translational modifications including heme-protein cross-links, with the underlying mechanisms not well understood. In this study, we introduced a Cys (K42C) close to the heme 4-vinyl group in sperm whale myoglobin (Mb) and solved its X-ray crystal structure. Interestingly, we found that K42C Mb can partially form a Cys-heme cross-link (termed K42C Mb-X) under dithiothreitol-induced reductive conditions in presence of O2, as suggested by guanidine hydrochloride-induced unfolding and heme extraction studies. Mass spectrometry (MS) studies, together with trypsin digestion studies, further indicated that a thioether bond is formed between Cys42 and the heme 4-vinyl group with an additional mass of 16Da, likely due to hydroxylation of the alphacarbon. We then proposed a plausible mechanism for the formation of the novel Cys-heme cross-link based on MS, kinetic UV-vis and electron paramagnetic resonance (EPR) studies. Moreover, the Cys-heme cross-link was shown to fine-tune the protein reactivity toward activation of H2O2. This study provides valuable insights into the post-translational modification of heme proteins, and also suggests that the Cys-heme cross-link can be induced to form in vitro, making it useful for design of new heme proteins with a non-dissociable heme and improved functions.

Formation of Cys-heme cross-link in K42C myoglobin under reductive conditions with molecular oxygen.,Cheng HM, Yuan H, Wang XJ, Xu JK, Gao SQ, Wen GB, Tan X, Lin YW J Inorg Biochem. 2018 Feb 19;182:141-149. doi: 10.1016/j.jinorgbio.2018.02.011. PMID:29477977^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.