Sandbox 300: Difference between revisions
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<Structure load='PDBREF' size='300' frame='true' align='right' caption='Staphylococcal protein A' scene='Insert optional scene name here' /> | <Structure load='PDBREF' size='300' frame='true' align='right' caption='Staphylococcal protein A' scene='Insert optional scene name here' /> | ||
Staphylococcal protein A is originally a component of the cell wall in over 90% of Staphylococcus aureus strains.This protein, which is also called immunoglobulin G binding protein A is covalently linked to the peptidoglycan of the cell wall. | Staphylococcal protein A is originally a component of the cell wall in over 90% of ''Staphylococcus aureus'' strains.This protein, which is also called immunoglobulin G binding protein A is covalently linked to the peptidoglycan of the cell wall. | ||
Nowadays the protein is often used for biochemical analysis due to its structural and biochemical properties. | Nowadays the protein is often used for biochemical analysis due to its structural and biochemical properties. | ||
The expression of the chromosomal spa gene, which encodes the protein A, is regulated by the agr system and Rot. The level of expression is up-regulated by Rot and down-regulated by agr. | The expression of the chromosomal spa gene, which encodes the protein A, is regulated by the ''agr'' system and Rot. The level of expression is up-regulated by Rot and down-regulated by ''agr''. | ||
Furthermore protein A serves as a virulence factor to Staphylococcus aureus . It is essential for the colonization and infections mediated by this kind of bacteria. | Furthermore protein A serves as a virulence factor to ''Staphylococcus aureus'' . It is essential for the colonization and infections mediated by this kind of bacteria. | ||
==Structure of the protein== | ==Structure of the protein== | ||
The structural details of protein A were solved by the nuclear magnetic resonance method. The length of the amino acid chain of protein A contains 508 residues. The amino acids cystein and tryptophan do not occur in the amino acid sequence. The molecular weight of the described protein is 55439 Dalton and it consists of only one protein chain. | The structural details of protein A were solved by the nuclear magnetic resonance method. The length of the amino acid chain of protein A contains 508 residues. The amino acids cystein and tryptophan do not occur in the amino acid sequence. The molecular weight of the described protein is 55439 Dalton and it consists of only one protein chain. | ||
The 3D structure is build up of three α-helixes and it consists of five extracellular domains, which are designated as E, D, A, B and C. Furthermore the protein contains cell-wall spanning regions, called | The 3D structure is build up of three α-helixes and it consists of five extracellular domains, which are designated as E, D, A, B and C. Furthermore the protein contains cell-wall spanning regions, called X'''r''' and X'''c''', and a hydrophobic membrane spanning domain, which is distal to LPXTG and consists of 18-20 residues ( Hartleib et al 2000 Protein A is the vWF binding protein on S. aureus). Protein A exists in a secreted and a cell wall anchored form. If it is bound to the cell wall of Staphylococcus aureus it is covalently linked to the peptidoglycan via its C-terminal domain. | ||