What a catch! Climate determinant structural differences in Atlantic Cod hemoglobin

Abstract

As the climate changes, we must understand the biology of our fish stocks to better support the conservation of our global fisheries. Gadus Morhau, commonly known as Atlantic Cod, differs from other tetrameric hemoglobin species in that one of the key packing contacts, Phenylalanine 122, is replaced by Leucine, changing the interaction between the key packing contacts and thus the overall structure of the hemoglobin. Additionally, due to a hemoglobin polymorphism, Atlantic Cod has multiple subpopulations, the most common of which are the homozygous genotypes Hbl‐1 and Hbl‐2. Hbl‐1 and Hbl‐2 genotypes differ due to a mutation in amino acid sequence on the β1 chain, in the Hbl‐1 genotype, at Methionine 55, Lysine 62, and Leucine 122 (as mentioned above). However, on the Hbl‐2 genotype, the amino acids in the corresponding locations are Valine 55, Alanine 62, and Methionine 122. These mutations result in a significant divergence in structure that completely changes the optimal living conditions for the fish. tThe ideal environmental temperatures for different types of Atlantic Cod, the Hbl‐2 allele has a frequency of 99% in northern regions, whereas the Hbl‐1 allele is more common in warmer areas, suggesting that the Hbl‐2 allele helps the fish adapt to colder temperatures. Furthermore, temperature seems to impact the oxygen affinity of the two genotypes. Due to its structure, Hbl‐2 has higher oxygen bonding affinity at temperatures 10 degrees Celsius and lower, whereas the Hbl‐1 allele functions more efficiently at temperatures 14 degrees Celsius or higher. Using JMol modeling software, we compared the structures of the Hbl‐1 to Hbl‐2 Atlantic Cod hemoglobins paying close attention to the relationship between substitutional packing contacts Leucine 122 in Hbl‐1 and Methionine 122 in Hbl‐2, and the commonality of contact amino acid, Arginine B12, which is located on the α1 chain of the hemoglobin. We used JMol to analyze how amino acid substitutions in the β1 chain of the Atlantic Cod cause significant structural differences that leads to variation in optimal living conditions; we infer those adaptations may prove advantageous to their survival in their extreme environments. The Mahtomedi MSOE Center for BioMolecular Modeling MAPS Team used 3‐D modeling and printing technology to examine the structure‐function relationships of the Atlantic Cod hemoglobin polymorphisms. The visual model will be a valuable tool in developing our story.