A novel two-over-two α-helical sandwich fold is characteristic of the truncated hemoglobin family

Alessandra Pesce, Manon Couture, Sylvia Dewilde, Michel Guertin, Kiyoshi Yamauchi, Paolo Ascenzi, Luc Moens, Martino Bolognesi

Research output: Contribution to journalArticlepeer-review


Small hemoproteins displaying amino acid sequences 20-40 residues shorter than (non-)vertebrate hemoglobins (Hbs) have recently been identified in several pathogenic and non-pathogenic unicellular organisms, and named 'truncated hemoglobins' (trHbs). They have been proposed to be involved not only in oxygen transport but also in other biological functions, such as protection against reactive nitrogen species, photosynthesis or to act as terminal oxidases. Crystal structures of trHbs from the ciliated protozoan Paramecium caudatum and the green unicellular alga Chlamydomonas eugametos show that the tertiary structure of both proteins is based on a 'two-over-two' α-helical sandwich, reflecting an unprecedented editing of the classical 'three-over-three' a-helical globin fold. Based on specific Gly-Gly moths the tertiary structure accommodates the deletion of the N-terminal A-helix and replacement of the crucial heme-binding F-helix with an extended polypeptide loop. Additionally, concerted structural modifications allow burying of the heme group and define the distal site, which hosts a TyrB10, GlnE7 residue pair. A set of structural and amino acid sequence consensus rules for stabilizing the fold and the bound heme in the trHbs homology subfamily is deduced.

Original languageEnglish
Pages (from-to)2424-2434
Number of pages11
JournalEMBO Journal
Issue number11
Publication statusPublished - Jun 1 2000


  • Chloroplast hemoglobin
  • Globin-fold evolution
  • Helical fold
  • Hemoglobins
  • Paramecium hemoglobin

ASJC Scopus subject areas

  • Genetics
  • Cell Biology


Dive into the research topics of 'A novel two-over-two α-helical sandwich fold is characteristic of the truncated hemoglobin family'. Together they form a unique fingerprint.

Cite this