Sandbox Reserved 335: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 18: | Line 18: | ||
<Structure load='3cp5' size='300' frame='true' align='right' caption='Figure 2' scene='Sandbox_Reserved_335/Heme/1' /> | <Structure load='3cp5' size='300' frame='true' align='right' caption='Figure 2' scene='Sandbox_Reserved_335/Heme/1' /> | ||
All members in the C-type cytochrome superfamily contain a heme prosthetic group that is covalently attached to the protein via two thioether bonds to cysteine residues. Most cytochromes ''c'' occur in a <scene name='Sandbox_Reserved_335/Motif/1'>CXXCH motif</scene> where a histidine residue is one of the two axial ligands of the heme iron.<ref name=main>PMID:18855424</ref><ref name=heme /> In monoheme cytochromes ''c'', the other axial position may be left vacant or be occupied by histidine or methionine residues; however, it can sometimes be occupied by cysteine or leucine residues.<ref name=main />. In ''Rm''cyt''c'', '''XX represents a threonine (Thr46) and an alanine residue (Ala47); these two residues are not involved in coordinating the iron ligand.''' The typical monoheme cyt ''c'' fold is formed by helices <scene name='Sandbox_Reserved_335/Helices/2'>A, C, and E</scene>. ''Rm''cyt''c'' contains seven α-helices that are folded around the heme, all connected by random coils.<ref name=main /> The heme group is axially coordinated by <scene name='Sandbox_Reserved_335/Axial/6'>His49 and Met100</scene>, and the disulfide linkages exist at <scene name='Sandbox_Reserved_335/Cys/1'>Cys45 and Cys48</scene> | All members in the C-type cytochrome superfamily contain a heme prosthetic group that is covalently attached to the protein via two thioether bonds to cysteine residues. Most cytochromes ''c'' occur in a <scene name='Sandbox_Reserved_335/Motif/1'>CXXCH motif</scene> where a histidine residue is one of the two axial ligands of the heme iron.<ref name=main>PMID:18855424</ref><ref name=heme /> In monoheme cytochromes ''c'', the other axial position may be left vacant or be occupied by histidine or methionine residues; however, it can sometimes be occupied by cysteine or leucine residues.<ref name=main />. In ''Rm''cyt''c'', '''XX represents a threonine (Thr46) and an alanine residue (Ala47); these two residues are not involved in coordinating the iron ligand.''' The typical monoheme cyt ''c'' fold is formed by helices <scene name='Sandbox_Reserved_335/Helices/2'>A, C, and E</scene>. ''Rm''cyt''c'' contains seven α-helices that are folded around the heme, all connected by random coils.<ref name=main /> The heme group is axially coordinated by <scene name='Sandbox_Reserved_335/Axial/6'>His49 and Met100</scene>, and the disulfide linkages exist at <scene name='Sandbox_Reserved_335/Cys/1'>Cys45 and Cys48</scene>. | ||
The heme group in ''Rm''cyt''c'' is almost completely shielded from solvent due to it being in a mostly hydrophobic pocket. This pocket is formed in part by the seven helices surrounding the ring, but also by two structures that are uncommon in cyt ''c''. | |||
The heme | |||
As determined by X-ray crystallography, the Rmcytc structure was found to also contain a coordinated sulfate ion; this ion has been seen to mediate crystal contact between neighbouring protein molecules. The carboxylate oxygen of Glu122 was also found to be involved in hydrogen bonding with this sulfate ion.<ref name=main /> | As determined by X-ray crystallography, the Rmcytc structure was found to also contain a coordinated sulfate ion; this ion has been seen to mediate crystal contact between neighbouring protein molecules. The carboxylate oxygen of Glu122 was also found to be involved in hydrogen bonding with this sulfate ion.<ref name=main /> | ||
