Dataset Information

Hypoxic survival requires a 2-on-2 hemoglobin in a process involving nitric oxide.

ABSTRACT: Hemoglobins are recognized today as a diverse family of proteins present in all kingdoms of life and performing multiple reactions beyond O2 chemistry. The physiological roles of most hemoglobins remain elusive. Here, we show that a 2-on-2 ("truncated") hemoglobin, termed THB8, is required for hypoxic growth and the expression of anaerobic genes in Chlamydomonas reinhardtii. THB8 is 1 of 12 2-on-2 hemoglobins in this species. It belongs to a subclass within the 2-on-2 hemoglobin class I family whose members feature a remarkable variety of domain arrangements and lengths. Posttranscriptional silencing of the THB8 gene results in the mis-regulation of several genes and a growth defect under hypoxic conditions. The latter is intensified in the presence of an NO scavenger, which also impairs growth of wild-type cells. As recombinant THB8 furthermore reacts with NO, the results of this study indicate that THB8 is part of an NO-dependent signaling pathway.

SUBMITTER: Hemschemeier A

PROVIDER: S-EPMC3696821 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Hypoxic survival requires a 2-on-2 hemoglobin in a process involving nitric oxide.

Hemschemeier Anja A Düner Melis M Casero David D Merchant Sabeeha S SS Winkler Martin M Happe Thomas T

Proceedings of the National Academy of Sciences of the United States of America 20130610 26

Hemoglobins are recognized today as a diverse family of proteins present in all kingdoms of life and performing multiple reactions beyond O2 chemistry. The physiological roles of most hemoglobins remain elusive. Here, we show that a 2-on-2 ("truncated") hemoglobin, termed THB8, is required for hypoxic growth and the expression of anaerobic genes in Chlamydomonas reinhardtii. THB8 is 1 of 12 2-on-2 hemoglobins in this species. It belongs to a subclass within the 2-on-2 hemoglobin class I family w ...[more]

PMID: 23754374

Similar Datasets

Project description:Mycobacterium tuberculosis group I truncated hemoglobin trHbN catalyzes the oxidation of nitric oxide (NO) to nitrate with a second-order rate constant k approximately 745 microM(-1) s(-1) at 23 degrees C (nitric oxide dioxygenase reaction). It was proposed that this high efficiency is associated with the presence of hydrophobic tunnels inside trHbN structure that allow substrate diffusion to the distal heme pocket. In this work, we investigated the mechanisms of NO diffusion within trHbN tunnels in the context of the nitric oxide dioxygenase reaction using two independent approaches. Molecular dynamics simulations of trHbN were performed in the presence of explicit NO molecules. Successful NO diffusion from the bulk solvent to the distal heme pocket was observed in all simulations performed. The simulations revealed that NO interacts with trHbN at specific surface sites, composed of hydrophobic residues located at tunnel entrances. The entry and the internal diffusion of NO inside trHbN were performed using the Long, Short, and EH tunnels reported earlier. The Short tunnel was preferentially used by NO to reach the distal heme pocket. This preference is ascribed to its hydrophobic funnel-shape entrance, covering a large area extending far from the tunnel entrance. This funnel-shape entrance triggers the frequent formation of solvent-excluded cavities capable of hosting up to three NO molecules, thereby accelerating NO capture and entry. The importance of hydrophobicity of entrances for NO capture is highlighted by a comparison with a polar mutant for which residues at entrances were mutated with polar residues. A complete map of NO diffusion pathways inside trHbN matrix was calculated, and NO molecules were found to diffuse from Xe cavity to Xe cavity. This scheme was in perfect agreement with the three-dimensional free-energy distribution calculated using implicit ligand sampling. The trajectories showed that NO significantly alters the dynamics of the key amino acids of Phe(62)(E15), a residue proposed to act as a gate controlling ligand traffic inside the Long tunnel, and also of Ile(119)(H11), at the entrance of the Short tunnel. It is noteworthy that NO diffusion inside trHbN tunnels is much faster than that reported previously for myoglobin. The results presented in this work shed light on the diffusion mechanism of apolar gaseous substrates inside protein matrix.

Dataset Information

Hypoxic survival requires a 2-on-2 hemoglobin in a process involving nitric oxide.

Publications

Hypoxic survival requires a 2-on-2 hemoglobin in a process involving nitric oxide.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets