Molecular cloning and 3D structure prediction of myoglobin and cytoglobin in Eurasian Tree Sparrow Passer montanus

Abstract

In vertebrates, myoglobin (Mb) and cytoglobin (Cygb) are closest relatives in the family of globins, which are heme-containing proteins that can bind gaseous molecules. Mb acts not only as an O2 transporter but also a nitric oxide (NO) scavenger in cardiac and striated muscle. Cygb has been suggested to play important functions in lipid-based signaling processes, defense against reactive oxygen species (ROS), and nitric oxide (NO) metabolism, and it is present in a variety of cell types. However, little information about the structures and functions of Mb and Cygb is known in birds. Here, we cloned the full-length open reading frames (ORFs) of the two globins in Eurasian Tree Sparrow (Passer montanus). The Mb ORF cDNA contains 465 base pairs (bp) encoding 154 amino acids (aa), and the Cygb ORF cDNA contains 540 bp encoding 179 aa. Our results show that the amino acid sequences and three-dimensional (3D) structures of Mb and Cygb are highly conserved in vertebrate species. Interestingly, two specific substitutions were detected in Cygb compared with other vertebrates, which resulted in slight variation of the 3D conformation (e.g., distance between Tyr H16 and Lys G8, the strength of hydrogen bonds, and angles between the G–H helices). Our results may contribute to further understanding the structures, properties, and functions of Mb and Cygb as well as the potential mechanisms of oxygen utilization pathways in vertebrates.