Nonsymbiotic haemoglobins in plants.

Abstract

General aspects regarding the presence of nonsymbiotic haemoglobin in plants are presented with the emphasis on those related to its function. As it becomes apparent that the nonsymbiotic haemoglobins are widespread across the plant kingdom and that they represent a more primitive and evolutionary older form of the plant globin genes, the question of their function becomes more attractive. While the physiological functions of the symbiotic haemoglobins in plants are well understood, almost nothing is known about their nonsymbiotic predecessors. Therefore, the known and hypothetical functions of haemoglobins in various systems are described along with information concerning properties and the regulation of expression of the nonsymbiotic haemoglobins. Interestingly, a number of nonsymbiotic haemoglobins have been shown to be hypoxia-inducible. The spatial and temporal pattern of this induction in barley may suggest that it is an integral part of the plants response to limiting oxygen stress.

Comparative kinetic analysis of anaerobic nitrite metabolism in phytoglobins

“…The pentacoordinate nature can also be detected within the absorbance spectra of the ferrous (reduced, Fe 2+ ) Lba as evidenced by a single peak in the visible region at 555 nm ( those classes being class 0, class 1, class 2, and class 3 (10). The biochemical and biophysical properties between the different classes of nsHbs vary, and so do their functions (6)(7)(8)(9).…”

“…Hemoglobins (Hbs) are a group of proteins that exist throughout all kingdoms of life (6)(7)(8)(9). The main role and function of Hb is that of an oxygen-sensing and binding protein, although other specialized functions have been attributed.…”

“…The main role and function of Hb is that of an oxygen-sensing and binding protein, although other specialized functions have been attributed. This protein type is best characterized as having a globin polypeptide encompassing a heme prosthetic group (6,8).…”

“…The overall protein structure of phytogbs can be described as traditional, with a globin polypeptide folded around a heme prosthetic group (6,8). The heme is a protoporphyrin ring with an Iron (Fe) ion in the center.…”

“…Dependent on the phytogb, the quaternary structure can be monomeric or a homodimer with a 1:1 ratio between the heme prosthetic group and globin (8,(12)(13)(14)17).…”