Tyrosinate (Tyr⁻)–ligated heme proteins exist in nature such as bovine liver catalase (BLC), coral allene oxide synthase (AOS) and several heme-transport proteins. AOS (~45 kDa) is a heme protein with sequence similarity to and catalytic functional difference from catalases. Recently, a new heme protein (AV protein, ~33 kDa) has been isolated from cattle pathogen Mycobacterium avium subspecies paratuberculosis. AV protein has sequence similarities to BLC and AOS (~25% amino acid identity), but distinct catalytic activities. Although it has weak catalase (catalatic) activity with H₂O₂, it exhibits significant peroxidase activity with organic hydroperoxides. As an extension of our study to probe the heme iron coordination modes in this group of heme proteins, we have characterized AV protein in comparison with AOS and BLC, whose structures are known, using magnetic circular dichroism (MCD) and UV-visible spectroscopic techniques in this study. AV protein shows spectroscopic properties remarkably similar to those of BLC in its native Fe(III) and Fe(III)-CN⁻ states, indicating that AV protein also contains a Tyr⁻-ligated heme. We have also found that, upon reduction, AV protein forms deoxyferrous and oxyferrous states whose spectra are similar to those of the corresponding states of His-ligated heme proteins such as horseradish peroxidase and myoglobin. AV protein also forms a 5-coordinate Fe(II)-NO complex in contrast to a 6-coordinate, presumably Tyr⁻-Fe(II)-NO complex of AOS. These results suggest that AV protein has a distal His like AOS and BLC and that the Tyr⁻ axial ligand in AV protein is relatively easily displaced in the ferrous state.