Haemoglobins of Mycobacteria: Structural Features and Biological Functions - Advances in Microbial Physiology - page 145

CHAPTER FIVE

Haemoglobins of Mycobacteria:
Structural Features and
Biological Functions

,1 , Kanak L. Dikshit †,1
* School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, University Park,
Nottingham, United Kingdom
† CSIR-Institute of Microbial Technology, Chandigarh, India
1 Corresponding authors: e-mail address: [e-mail]; [e-mail]

Kelly S. Davidge *

Contents
1.

Introduction: Discovery of Haemoglobins in Mycobacteria 148

2. Co-occurrence of Multiple Hbs in Mycobacteria 149

3. trHbs of Mycobacteria: Small Hbs with Novel Characteristics 152

3.1 Group I trHbs: trHbN 153

3.2 Group II trHbs: trHbO 163

3.3 Type III trHbs: trHbP 169

3.4 Genetic regulation of the trHbs 169

4. Conventional and Novel FlavoHbs of Mycobacteria 173

4.1 Structural features 174

4.2 Functional properties 180

4.3 Genomic organisation and genetic regulation 180

5. Biological Functions of trHbs and FlavoHbs 182

5.1 Nitric oxide scavenging 182

5.2 Oxygen metabolism 186

5.3 Redox signalling and stress management 188

5.4 Other functions 188

6. Concluding Remarks 189

References 189

Abstract
The genus Mycobacterium is comprised of Gram-positive bacteria occupying a wide
range of natural habitats and includes species that range from severe intracellular path-
ogens to economically useful and harmless microbes. The recent upsurge in the avail-
ability of microbial genome data has shown that genes encoding haemoglobin-like
proteins are ubiquitous among Mycobacteria and that multiple haemoglobins (Hbs)
of different classes may be present in pathogenic and non-pathogenic species. The
occurrence of truncated haemoglobins (trHbs) and flavohaemoglobins (flavoHbs)
showing distinct haem active site structures and ligand-binding properties suggests