FtsA plays an essential role in Escherichia coli cell division and is nearly ubiquitous in eubacteria. Several evidences postulated the ability of FtsA to interact with other septation proteins and with itself. To investigate these binding properties, we screened a phage‐display library with FtsA. The isolated peptides defined a degenerate consensus sequence, which in turn displayed a striking similarity with residues 126–133 of FtsA itself. This result suggested that residues 126–133 were involved in homodimerization of FtsA. The hypothesis was supported by the analysis of correlated mutations, which identified a mutual relationship between a group of amino acids encompassing the ATP‐binding site and a set of residues immediately downstream to amino acids 126–133. This information was used to assemble a model of a FtsA homodimer, whose accuracy was confirmed by probing multiple alternative docking solutions. Moreover, a prediction of residues responsible for protein‐protein interaction validated the proposed model and confirmed once more the importance of residues 126–133 for homodimerization. To functionally characterize this region, we introduced a deletion in ftsA, where residues 126–133 were skipped. This mutant failed to complement conditional lethal alleles of ftsA, demonstrating that amino acids 126–133 play an essential role in E. coli. Proteins 2003;50:192–206. © 2002 Wiley‐Liss, Inc.

ABSTRACT We analyzed the chromosome region of Streptococcus pneumoniae located downstream of the division and cell wall ( dcw ) cluster that contains the homolog of the Bacillus subtilis cell division gene divIVA and some genes of unknown function. Inactivation of divIVA in S. pneumoniae resulted in severe growth inhibition and defects in cell shape, nucleoid segregation, and cell division. Inactivation of the ylm genes resulted in some morphological and/or division abnormalities, depending on the inactivated gene. Transcriptional analysis revealed a relationship between these genes and the ftsA and ftsZ cell division genes, also indicating that the connection between the dcw cluster and the divIVA region is more extensive than just chromosomal position and gene organization.

The genes responsible for cell wall biosynthesis and cell division (dcw genes) were identified and sequenced in Streptococcus pneumoniae. The genetic organization of the dcw cluster in Streptococcus pneumoniae differed significantly from the clusters of other bacteria reported to date. In particular, the genes corresponding to the 2 min region of the Escherichia coli chromosome were found distributed in three genetically separate regions of the Streptococcus pneumoniae chromosome. The first region contained the expected ftsA and ftsZ cell division genes at one end and pbp2b, ddl and murF at the other end. The murD, murG and divIB genes, always found located upstream of ftsA, were found in a second region separated from the first. A third region contained the yllC, yllD, pbp2x and mraY genes. The chromosomal region downstream of ftsZ was also sequenced and characterized. In Streptococcus pneumoniae this region contains four ORFs, all of unknown function, and an ORF encoding the Bacillus subtilis DivIVA homologue. The gene order and the organization of this region was found to be conserved in Staphylococcus aureus, Streptococcus pyogenes and Bacillus subtilis, raising the possibility that previously unidentified loci may also be involved in division.

Pseudo-tri- and -tetra-peptide aminoalkylphosphinic acids of general structure X-Lys-PO2H-Gly-Ala have been synthesised as transition state analogues for D-Ala-D-Ala adding enzyme, The key synthetic step used to assemble the C-terminal dipeptide unit is a modified Arbusov reaction, coupling bromopropionyl-D-alanine methyl ester to a silylated aminoalkylphosphonite. Kinetic assays with the purified E. coli enzyme reveal that the phosphinate analogues act as reversible competitive inhibitors, with K-i values in the range 200-700 mu M. Extended analogues mimicking the peptide chain of the UDPMurNAc-L-Ala-gamma-D-Glu-m-DAP substrate show increased binding affinity for the enzyme active site. These are the first reported inhibitors for D-Ala-D-Ala adding enzyme.