THE NON-PENICILLIN-BINDING MODULE OF THE TRIPARTITE PENICILLIN-BINDING PROTEIN 3 OF ESCHERICHIA-COLI IS REQUIRED FOR FOLDING AND OR STABILITY OF THE PENICILLIN-BINDING MODULE AND THE MEMBRANE-ANCHORING MODULE CONFERS CELL SEPTATION ACTIVITY ON THE FOLDED STRUCTURE/
C. Goffin et al., THE NON-PENICILLIN-BINDING MODULE OF THE TRIPARTITE PENICILLIN-BINDING PROTEIN 3 OF ESCHERICHIA-COLI IS REQUIRED FOR FOLDING AND OR STABILITY OF THE PENICILLIN-BINDING MODULE AND THE MEMBRANE-ANCHORING MODULE CONFERS CELL SEPTATION ACTIVITY ON THE FOLDED STRUCTURE/, Journal of bacteriology, 178(18), 1996, pp. 5402-5409
The ftsI-encoded multimodular class B penicillin-binding protein 3 (PB
P3) is a kev dement of the cell septation machinery of Escherichia col
i. Altered ftsI genes were overexpressed, and the gene products were a
nalyzed with respect to the level of production, stability, penicillin
affinity, and cell septation activity. In contrast to the serine beta
-lactamases and low-molecular-mass PBPs which are autonomous folding e
ntities, the S-259-to-V-577 penicillin-binding module of M-1-to-V-577
PBP3 lacks the amino acid sequence information for correct folding, Th
e missing piece of information is provided by the associated G-57-to-E
-258 non-penicillin-binding module which functions as a noncleaved, ps
eudointramolecular chaperone. Key elements of the folding information
reside within the motif 1-containing R-60-to-W-110 polypeptide segment
and within G-188-to-D-197 motif 3 of the n-PB module. The intermodule
interaction is discussed in the light of the known three-dimensional
structure (at 3.5-Angstrom [0.35-nm] resolution) of the analogous clas
s B PBP2x of Streptococcus pneumoniae (S. Pares, N. Mouz, Y. Petillot,
R, Hakenbeck, and O. Dideberg, Nature Struct. Biol, 3:284-289, 1996),
Correct folding and adoption of a stable penicillin-binding conformat
ion are necessary but not sufficient to confer cell septation activity
to PBP3 in exponentially growing cells, The in vivo activity of PBP3
also depends on the M-1-to-E-56 amino-terminal module which encompasse
s the cytosol, the membrane, and the periplasm and which functions as
a noncleaved pseudo-signal peptide.