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Truncated hemoglobins: trimming the classical ‘three‐over‐three’ globin fold to a minimal size
Author(s) -
Milani Mario,
Pesce Alessandra,
Bolognesia Martino,
Ascenzi Paolo
Publication year - 2001
Publication title -
biochemistry and molecular biology education
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.34
H-Index - 39
eISSN - 1539-3429
pISSN - 1470-8175
DOI - 10.1111/j.1539-3429.2001.tb00093.x
Subject(s) - globin , antiparallel (mathematics) , fold (higher order function) , crystallography , heme , chemistry , biophysics , hemoglobin , biology , physics , computer science , biochemistry , enzyme , quantum mechanics , magnetic field , programming language
Truncated hemoglobins (trHbs) host the heme in a ‘two‐over‐two’ α‐helical sandwich which results from extensive editing of the classical ‘three‐over‐three’ globin fold. The three‐dimensional structure of trHbs is based on four main α‐helices, arranged in a sort of α‐helical bundle composed of two antiparallel helix pairs (B/E and G/H). Most notably, trHbs deviate from the conventional globin fold in that they display an extended loop substituting for the heme proximal F‐helix observed in globins. Moreover, since efficient adaptation of a 110–130 amino acid trHb chain to host the porphyrin ring firstly requires specific chain flexibility, trHbs contain three invariant Gly‐based motifs. Inspection of the trHb three‐dimensional trHb structures shows that an apparent protein cavity or tunnel would connect the protein surface to an inner region very close to the heme distal site. Such a structural feature, never observed before in (non) vertebrate globins, may have substantial implications for ligand diffusion and binding properties in trHbs. © 2001 IUBMB. Published by Elsevier Science Ltd. All rights reserved.