Diversity of Globins in Myxobacteria.

Globins are heme proteins that are capable of reversible oxygen binding. All globins can be classified into three families: the M (myoglobin-like), S (sensor) and T (truncated) globins. M and S globins exhibit the canonical 3/3 α-helical fold, and T globins are characterized by a 2/2 α-helical fold. Globins in the genomes of myxobacteria have not been characterized till date. Myxobacteria have very large genomes relative to other bacteria and have a unique life cycle that involves the aggregation of cells into fruiting bodies under starvation conditions. The diversity of globin like sequences in 14 sequenced genomes of myxobacteria is presented in this review. In myxobacterial globins some unusual domain architectures are identified that have not been characterized in bacteria so far; these are: i) a unique chimeric group I 2/2 HbN in the genome of Corallococcus coralloides DSM 2259; ii) M globin chimera harboring a central and a C-terminal globin domain in Sorangium cellulosum ‘so ce 56’ and Plesiocystis pacifica SIR-1 respectively; iii) two tandem globin domains on the same M globin polypeptide in the genomes of Sorangium cellulosum.