Truncated hemoglobins, group 2 (O); Pseudoalteromonas haloplanktis PhHbO like
The M- and S families exhibit the canonical secondary structure of hemoglobins, a 3-over-3 alpha-helical sandwich structure (3/3 Mb-fold), built by eight alpha-helical segments. Truncated hemoglobins (TrHbs, 2/2Hb, or 2/2 globins) or the T family globins adopt a 2-on-2 alpha-helical sandwich structure, resulting from extensive and complex modifications of the canonical 3-on-3 alpha-helical sandwich that are distributed throughout the whole protein molecule. TrHbs are classified into three main groups based on their structural properties and named after Mycobacterium sp. genes glbN, glbO, and glbP: TrHb1s (N), TrHb2s (O) and TrHb3s (P). TrHb2's belonging to this group include Pseudoalteromonas haloplanktis PhHbO (encoded by the PSHAa0030 gene) which appears to be involved in oxidative and nitrosative stress resistance.
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