Functional diversification of myoglobin in the lungfish

• Applicant: Professor Dr. Thorsten Burmester
• Subject Area: Animal Physiology and Biochemistry
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263938600

Myoglobin is a respiratory protein that has served as model system in a variety of biological fields. Its main function is to deliver and store O2 in the heart and skeletal) muscles. Myoglobin may also act as an enzyme and is instrumental in homeostasis of nitric oxide (NO) and detoxification of reactive oxygen species (ROS). Almost any vertebrate harbors only a single myoglobin gene; only some cyprinid fish have two myoglobin genes. In addition, expression of myoglobin outside the muscles has rarely been observed. We have found that the West African lungfish Protopterus annectens harbors at least seven distinct myoglobin genes that are differentially expressed in various tissues. Lungfishes occupy a key position for the understanding of tetrapod evolution and terrestrialization. The unexpected diversity of myoglobin strongly hints to subfunctionalization and/or neofunctionalization of this gene in the lungfish. The objective of this application is to understand the functional diversity of lungfish myoglobins and its emergence. We will measure the O2 binding kinetics of recombinantly expressed myoglobin, analyze their enzymatic activities, and study their tissue and cellular distributions. Additional analyses will be carried out in stably transfected vertebrate cell lines: the ability of different myoglobins to augment mitochondrial respiration, to mediate tolerance towards hypoxia and ROS, to protect from apoptosis and their roles in the generation of NO will be tested. The combination of the results from these experiments will allow us to identify the function of each single lungfish myoglobin and help to understand their functional diversification in evolution.

• DFG Programme: Research Grants