Sandbox 124: Difference between revisions
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peptidoglycan cross-linked together with pentaglycine chains. The NAM residues | peptidoglycan cross-linked together with pentaglycine chains. The NAM residues | ||
have a five amino acid side chain that terminates with two D-Alanine (D-Ala) | have a five amino acid side chain that terminates with two D-Alanine (D-Ala) | ||
residues. | residues. [[Image:Cell Wall 7 30 2013.jpg|thumb|alt= Alt text| | ||
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==='''Catalytic Mechanism of PBP2a'''=== | ==='''Catalytic Mechanism of PBP2a'''=== | ||
(a) The D-Ala-D-Ala side-chain substrate of the peptidoglycan accesses the active site of | (a) The D-Ala-D-Ala side-chain substrate of the peptidoglycan accesses | ||
the PBP2a. | the active site of the PBP2a. | ||
(b) Ser403 nucleophilically attacks the peptide bond of the terminal D-Ala residues of the | (b) Ser403 nucleophilically attacks the peptide bond of the terminal | ||
substrate. The terminal D-Ala residue then exits the active site. | D-Ala residues of the substrate. The terminal D-Ala residue then exits | ||
(c) The now terminal D-Ala residue forms a covalent bond to Ser403, while a crosslinking | the active site. | ||
pentaglycine chain enters the active site. | (c) The now terminal D-Ala residue forms a covalent bond to Ser403, | ||
(d) A covalent bond forms between the pentaglycine chain and the terminal D-Ala | while a crosslinking pentaglycine chain enters the active site. | ||
residue, regenerating the active site serine residue. | (d) A covalent bond forms between the pentaglycine chain and the | ||
terminal D-Ala residue, regenerating the active site serine residue. | |||
The entire process takes 4 milliseconds. | The entire process takes 4 milliseconds. | ||
