Non-Heme Protein in the Giant Extracellular Hemoglobin of the Earthworm Lumbricus terrestris

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 85; no. 24; pp. 9461 - 9463
• Main Authors: Fushitani, Kenzo, Riggs, Austen F.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.12.1988; National Acad Sciences
• Subjects: Amino acids; Animals; Biochemistry; Biochemistry. Physiology. Immunology; Biological and medical sciences; Earthworms; Fundamental and applied biological sciences. Psychology; Heme - analysis; hemoglobin; Hemoglobins; Hemoglobins - analysis; Invertebrates; Ligands; Lumbricus terrestis; Macromolecular Substances; Molecular chains; Molecular Weight; Molecules; Mollusca; Oligochaeta; Physiology. Development; Sequencing; Terminology; Trimers; Binding protein; Molecular structure; Heme; Hemoglobin; Invertebrata; Extracellular; Annelida; Oligochaeta; Aminoacid sequence; Lumbricus terrestris
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.85.24.9461

The protein/heme mass ratio for the extracellular hemoglobin of the earthworm Lumbricus terrestris has been redetermined. We find a value of 19,000 g of protein per mol of heme. Four major, heme-containing chains (a, b, c, and d), present in equal proportions, have a total molecular mass, with four hemes, of 69,664 Da based on their sequences. The intact hemoglobin comprises 12 subunits that form a two-layered hexagonal structure of about 3.8 MDa. This value, together with our determination of the protein/heme ratio, requires that 4 abcd units are present in each 1/12th subunit and that 192 heme-containing chains are present in the hemoglobin molecule. Our data indicate that ≈ 2200 g of non-heme protein is present for each mole of heme-containing chain, or about 35,200 g per 1/12th subunit. This conclusion is consistent with the observation that chains of 31-37 kDa are present. On this basis the intact molecule would have 12 non-heme chains and 204 chains in all to give a total molecular mass of 3.77 MDa, close to that observed.