N-TERMINAL AMINO-ACID SEQUENCE OF THE DEEP-SEA TUBE WORM HEMOGLOBIN REMARKABLY RESEMBLES THAT OF ANNELID HEMOGLOBIN

  • 15 October 1988
    • journal article
    • research article
    • Vol. 255  (2) , 541-545
Abstract
The deep-sea giant tube worm Lamellibrachia, belonging to the phylum Vestimentifera, contains two extracellular haemoglobins, an Mr 3000000 haemoglobin and an Mr 440000 haemoglobin. The former has a hexagonal bilayer structure and consists of six polypeptide chains (AI-VI); a study of its haem content shows that not all of the chains contain haem. The Mr 440000 haemoglobin consists of four haem-containing chains(BI-IV). We isolated most of the chains by reverse-phase chromatography and determined the amino acid sequences of the 21-45 N-terminal residues. Eight chains (AI-IV and BI-IV) showed significant homology with haem-containing chains of annelid giant haemoglobin. The highest homology was found between Lamellibrachia chain AI and Tylorrhynchus chain I; surprisingly, 18 out of the 20 N-terminal residues are identical. On the other hand, chain AV, with an unusual Mr of 32000, showed a rather different sequence and is likely to be a non-haem chain which might act as a linker protein in the assembly of the haem-containing chains. From these results, we conclude that the tube worm Mr 3000000 haemoglobin is highly homologous with annelid haemoglobin.