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The amino acid sequence of hemoglobin III from the symbiont-harboring clam Lucina pectinata
J D Hockenhull-Johnson1, M S Stern, J B Wittenberg
1Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201.
Abstract:
The cytoplasmic hemoglobin III from the gill of the symbiont-harboring clam Lucina pectinata consists of 152 amino acid residues, has a calculated Mm of 18,068, including heme, and has N-acetyl-serine as the N-terminal residue. Based on the alignment of its sequence with other vertebrate and nonvertebrate globins, it retains the invariant residues Phe45 at position CD1 and His98 at the proximal position F8, as well as the highly conserved Trp16 and Pro39 at positions A12 and C2, respectively. The most likely candidate for the distal residue at position E7 is Gln66. Lucina hemoglobin III shares 95 identical residues with hemoglobin II (J. D. Hockenhull-Johnson et al., J. Prot. Chem. 10, 609-622, 1991), including Tyr at position B10, which has been shown to be capable of entering the distal heme cavity and placing its hydroxyl group within a 2.8 A of the water molecule occupying the distal ligand position, by modeling the hemoglobin II sequence using the crystal structure of sperm whale metmyoglobin. The amino acid sequences of the two Lucina globins are compared in detail with the known sequences of mollusc globins, including seven cytoplasmic and 11 intracellular globins. Relative to 75% homology between the two Lucina globins (counting identical and conserved residues), both sequences have percent homology scores ranging from 36-49% when compared to the two groups of mollusc globins. The highest homology appears to exist between the Lucina globins and the cytoplasmic hemoglobin of Busycon canaliculatum.
Insights
Cytoplasmic hemoglobin III from the clam Lucina pectinata has 152 amino acids and retains key conserved residues found in other globins. This hemoglobin shows high similarity to Lucina hemoglobin II and other mollusc globins.
Area of Science:
- Biochemistry
- Molecular Biology
- Marine Biology
Background:
- The study focuses on cytoplasmic hemoglobin III from the gill of the symbiont-harboring clam Lucina pectinata.
- Hemoglobins are crucial for oxygen transport in various organisms.
Purpose of the Study:
- To characterize the primary structure and sequence of Lucina pectinata cytoplasmic hemoglobin III.
- To compare its sequence with other known vertebrate and non-vertebrate globins, particularly mollusc hemoglobins.
Main Methods:
- Amino acid sequence alignment of Lucina hemoglobin III with other globins.
- Identification of conserved and invariant residues.
- Homology analysis with known mollusc globins.
Main Results:
- Lucina hemoglobin III consists of 152 amino acid residues with a molecular mass of 18,068 Da (including heme).
- It retains invariant residues (Phe45, His98) and conserved residues (Trp16, Pro39) common in globins.
- High sequence identity (95 residues) was found with Lucina hemoglobin II.
- Homology scores with other mollusc globins ranged from 36-49%, with highest similarity to Busycon canaliculatum cytoplasmic hemoglobin.
Conclusions:
- Lucina hemoglobin III exhibits structural features characteristic of globins.
- Its sequence comparison provides insights into the evolutionary relationships among mollusc globins.