A Comparative Study of the 3D Structure of Myoglobin and its Affect on the Physiology of Terrestrial and Aquatic Mammals

Abstract

Sperm whales dive deeper than two kilometers and swim for up to 90 minutes while searching for prey. Underwater, they depend on previously inhaled oxygen molecules. Myoglobin (Mb) contributes to this process by binding and storing oxygen until the time of need, and then releasing it, providing oxygen within muscle cells for aerobic respiration. Although the molecular structure of Mb was solved more than five decades ago, its unique connection to the physiology of underwater lifestyles has only recently come to light. Surprisingly, aquatic and terrestrial mammals differ in the net surface charge (Z) of their Mb protein, as calculated by summing up all the positively and negatively charged surface residues. For instance, sperm whales' Mb (pdb 1MBN) has a Z of +4, while aardvarks' Mb has a Z of +0.25. It thus seems possible that aquatic mammals' larger oxygen supply results from their Mb's greater net surface charge, as the greater the net surface charge leads to more repulsion between Mb proteins and subsequent increase in the amount of Mb which may be packed into each cell. Terrestrial animals have myoglobin with a more neutral net surface charge and therefore cannot increase oxygen storage in muscle by increasing the number of Mb, since the Mb will stick to each other at high concentrations. The Hostos‐Lincoln Academy SMART (Students Modeling A Research Topic) Team created a physical model using 3D printing technology of an alignment of sperm whale Mb pdb file 1MBN and aardvark Mb, pdb file 1EMY. We further compared multiple Mb structures of aquatic and terrestrial mammals to verify the significance of Mb net surface charge to the physiology of deep diving mammals.