Sandbox 127: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 30: | Line 30: | ||
[[Image:Structures on penicillin and b lactam.jpg|thumb|alt= Alt text|Figure 3. Mechanism of action of β-lactams. A. Structure of a β-lactam (penicillin) showing the amide, carboxyl, and β-lactam ring groups β-lactam ring groups. B. Structure of the D-Ala-D-Ala substrate. C. Overlay of the D-Ala-D-Ala substrate in red with penicillin demonstrating molecular mimicry.|550 px]] | [[Image:Structures on penicillin and b lactam.jpg|thumb|alt= Alt text|Figure 3. Mechanism of action of β-lactams. A. Structure of a β-lactam (penicillin) showing the amide, carboxyl, and β-lactam ring groups β-lactam ring groups. B. Structure of the D-Ala-D-Ala substrate. C. Overlay of the D-Ala-D-Ala substrate in red with penicillin demonstrating molecular mimicry.|550 px]] | ||
== Structure of PBP2a, a B-lactam Resistant Transpeptidase== | |||
Isolates of methicillin-resistant S. aureus (MRSA) are resistant to almost all currently available B-lactam because they have acquired an alternative PBP, PBP2a(encoded by the mecA gene), that is neither bound nor inhibited by B-lactams. PBP2a is composed of two domains:a a <font color='orange'><b>non-penicillin binding domain </b><scene name='36/365380/4dki_cartoon/17'>(NPB) </scene></font> and a <font color='dodgerblue'><b>transpeptidase <scene name='36/365380/4dki_cartoon/18'>(TP)</scene> binding domain </b></font>non-penicillin binding domain (NPB) and a TP-binding domain. The NPB domain of PBP2a is anchored in the cell membrane, while the TP domain resides in the periplasm with its active site facing the inner surface of the cell wall. The active site contains a serine residue at position 403 (Ser403) which catalyzes the cross-linking of the peptidoglycan rows with pentaglycine cross-links. | |||
