Sandbox Reserved 640: Difference between revisions

Line 38:

The <scene name='Sandbox_Reserved_640/Heme/1'>heme</scene> prosthetic group consists of four 5-membered pyrrole rings, forming a cyclic ring around a central iron (Fe) atom. This atom is contained within four equatorial nitrogens, in addition to another nitrogen from a close histidine residue and an opposite dioxygen (Ref 9). The ligand contact residues along the heme group are Phe30, His63, His97, and Val67. Depending on the specific type of Leghemoglobin, some of these specific residues are disordered and others interconvert between two conformations (Ref 7).

In opposition to the differences in polypeptides among globin proteins (Hemoglobin and Myoglobin), the heme group has been found to remain largely the same (Ref 1). The main difference is a considerably larger heme group in Leghemoglobin than its other oxygen-transferring counterparts. The way the heme group attaches to the polypeptide is also different. The steric crowding around the ligand binding site (beside the heme) is reduced, plus there is an altered packing at the proximal side of the heme and conformational differences along the distal side. As a result, the oxygen affinity is larger than that of Myoglobin and Hemoglobin (Ref 8).

In opposition to the differences in polypeptides among globin proteins (Hemoglobin and Myoglobin), the heme group has been found to remain largely the same (Ref 1). The main difference is a considerably larger heme group in Leghemoglobin than its other oxygen-transferring counterparts. The way the heme group attaches to the polypeptide is also different. The steric crowding around the ligand binding site (beside the heme) is reduced, plus there is an altered packing at the proximal side of the heme and conformational differences along the distal side. As a result, the oxygen affinity is larger than that of Myoglobin and Hemoglobin (Ref 8). This is reflected by the Km of 0.01 microM (the concentration for half of the Leghemoglobin to be saturated with dioxygen), about ten times the Michaelis constant for Hemoglobin (Ref 7).

The methods by which various Leghemoglobins were purified, and then analyzed, are as follows:

Sandbox Reserved 640: Difference between revisions

Navigation menu

Page actions

Page actions

Personal tools

Navigation

Search

Tools

@@ Line 38: / Line 38: @@
 The <scene name='Sandbox_Reserved_640/Heme/1'>heme</scene> prosthetic group consists of four 5-membered pyrrole rings, forming a cyclic ring around a central iron (Fe) atom.  This atom is contained within four equatorial nitrogens, in addition to another nitrogen from a close histidine residue and an opposite dioxygen (Ref 9).  The ligand contact residues along the heme group are Phe30, His63, His97, and Val67.  Depending on the specific type of Leghemoglobin, some of these specific residues are disordered and others interconvert between two conformations (Ref 7).
-In opposition to the differences in polypeptides among globin proteins (Hemoglobin and Myoglobin), the heme group has been found to remain largely the same (Ref 1).  The main difference is a considerably larger heme group in Leghemoglobin than its other oxygen-transferring counterparts.  The way the heme group attaches to the polypeptide is also different.  The steric crowding around the ligand binding site (beside the heme) is reduced, plus there is an altered packing at the proximal side of the heme and conformational differences along the distal side.  As a result, the oxygen affinity is larger than that of Myoglobin and Hemoglobin (Ref 8).
+In opposition to the differences in polypeptides among globin proteins (Hemoglobin and Myoglobin), the heme group has been found to remain largely the same (Ref 1).  The main difference is a considerably larger heme group in Leghemoglobin than its other oxygen-transferring counterparts.  The way the heme group attaches to the polypeptide is also different.  The steric crowding around the ligand binding site (beside the heme) is reduced, plus there is an altered packing at the proximal side of the heme and conformational differences along the distal side.  As a result, the oxygen affinity is larger than that of Myoglobin and Hemoglobin (Ref 8).  This is reflected by the Km of 0.01 microM (the concentration for half of the Leghemoglobin to be saturated with dioxygen), about ten times the Michaelis constant for Hemoglobin (Ref 7).
 The methods by which various Leghemoglobins were purified, and then analyzed, are as follows: