PMC

Heme displacement. (a) The heme in MAP_2744c (C, yellow) is displaced from its position in the cAOS structure (C, green). (b) Phe residues that impact heme placement. MAP_2744c, yellow, cAOS, green, catalase (HEC), blue.

The heme environment. The side chains of MAP_2744c (C, yellow) and cAOS (C, green) that surround the heme (space-filled rendering, C, white, N, blue, O, red, and Fe, magenta).

Access to heme. (a) A surface rendering of the MAP_2744c enzyme. The heme, in sphere rendering (Fe, white; C, N black) lies at the bottom of a large, deep cavity. (b) A stick rendering of cAOS is superposed on the MAP_2744c surface rendering. The presence of the additional side chain and main chain atoms in cAOS obstructs heme access.

The structure of MAP_2744c, a catalase-related enzyme. (a) Cartoon rendering of MAP_2744c. Coloring is N→C blue→red. The heme is depicted in space-filled rendering. (b) cAOS (white) superimposed on MAP_2744c. For clarity only the secondary structural elements of cAOS are drawn. (c) A structure based sequence alignment for MAP_2744c, cAOS, and HEC sequences. Those amino acids which are identical in the sequences are indicated in black boxes, while empty boxes indicate conservative substitutions. The elements of secondary structure are labeled according to their location in MAP_2744c.

Phylogenetic tree of MAP-2744c and related proteins. A TBLASTN database search was conducted using the peptide sequence of MAP-2744c as bait. The amino acid sequences of the proteins identified were entered in the MegAlign program of DNAStar which compiled the phylogenetic tree. Human catalase and cAOS were not found in the TBLASTN search and were added prior to the alignment. The two lower groups correspond to the catalases with “small” and “large” subunits as deduced by Klotz and Loewen. On top are two new groups comprising mini-sized catalases with polypeptides of 330–360 and 300–330 amino acids. MAP-2744c segregates with the 300–330 amino acid subgroup from gram positive (+ve) bacteria.