Abstract

Truncated hemoglobins (trHbs) host the heme in a "two-over-two' -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 -helices, arranged in a sort of -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.

Abbreviations: Hb, Hemoglobin; FlavoHb, Flavohemoglobin; TrHb, Truncated hemoglobin

¹These authors contributed equally to this work.

^*Corresponding author. Tel.: +39-06-5517-6329; fax: +39-06-5517-6321

[Full text] (PDF 147.2 Kb)

© Copyright 2008, Elsevier Science, All rights reserved.