Cloning and sequencing of the cell division gene pbpB, which encodes penicillin-binding protein 2B in Bacillus subtilis

531

489

SUMMARY In order to maintain shape and withstand intracellular pressure, most bacteria are surrounded by a cell wall that consists mainly of the cross-linked polymer peptidoglycan (PG). The importance of PG for the maintenance of bacterial cell shape is underscored by the fact that, for various bacteria, several mutations affecting PG synthesis are associated with cell shape defects. In recent years, the application of fluorescence microscopy to the field of PG synthesis has led to an enormous increase in data on the relationship between cell wall synthesis and bacterial cell shape. First, a novel staining method enabled the visualization of PG precursor incorporation in live cells. Second, penicillin-binding proteins (PBPs), which mediate the final stages of PG synthesis, have been localized in various model organisms by means of immunofluorescence microscopy or green fluorescent protein fusions. In this review, we integrate the knowledge on the last stages of PG synthesis obtained in previous studies with the new data available on localization of PG synthesis and PBPs, in both rod-shaped and coccoid cells. We discuss a model in which, at least for a subset of PBPs, the presence of substrate is a major factor in determining PBP localization.

Section: Localization Of Peptidoglycan Synthesismentioning

confidence: 99%

Bacterial Cell Wall Synthesis: New Insights from Localization Studies

Scheffers

Pinho

2005

531

489

“…Finally, the fourth major class of signal peptides is found on ribosomally synthesized bacteriocins and pheromones that are exported by ABC transporters (11,203,335). These signal peptides lack a hydrophobic H-domain and are removed from the mature protein by a subunit of the ABC transporter that is responsible for the export of a particular bacteriocin or pheromone or by specific SPases.…”

Section: Signal Peptide Classificationmentioning

confidence: 99%

Signal Peptide-Dependent Protein Transport in Bacillus subtilis : a Genome-Based Survey of the Secretome

Tjalsma

Bolhuis

Jongbloed

et al. 2000

747

768

SUMMARY One of the most salient features of Bacillus subtilis and related bacilli is their natural capacity to secrete a variety of proteins into their environment, frequently to high concentrations. This has led to the commercial exploitation of bacilli as major “cell factories” for secreted enzymes. The recent sequencing of the genome of B. subtilis has provided major new impulse for analysis of the molecular mechanisms underlying protein secretion by this organism. Most importantly, the genome sequence has allowed predictions about the composition of the secretome, which includes both the pathways for protein transport and the secreted proteins. The present survey of the secretome describes four distinct pathways for protein export from the cytoplasm and approximately 300 proteins with the potential to be exported. By far the largest number of exported proteins are predicted to follow the major “Sec” pathway for protein secretion. In contrast, the twin-arginine translocation “Tat” pathway, a type IV prepilin-like export pathway for competence development, and ATP-binding cassette transporters can be regarded as “special-purpose” pathways, through which only a few proteins are transported. The properties of distinct classes of amino-terminal signal peptides, directing proteins into the various protein transport pathways, as well as the major components of each pathway are discussed. The predictions and comparisons in this review pinpoint important differences as well as similarities between protein transport systems in B. subtilis and other well-studied organisms, such as Escherichia coli and the yeast Saccharomyces cerevisiae. Thus, they may serve as a lead for future research and applications.

“…In the gram-positive sporeforming organism Bacillus subtilis, the genes encoding the PBP fusions Bsu2b of subclass B4 (249) and BsuVD (encoded by spoVD) of subclass B3 (42) occur in tandem in the dcw cluster (43). The essential Bsu2b is produced during both vegetative growth and sporulation.…”

Section: Class a Pen R Protein Fusions Of Gram-negative Bacteriamentioning

confidence: 99%

Biochemistry and Comparative Genomics of SxxK Superfamily Acyltransferases Offer a Clue to the Mycobacterial Paradox: Presence of Penicillin-Susceptible Target Proteins versus Lack of Efficiency of Penicillin as Therapeutic Agent

Goffin

Ghuysen

2002

179

213

The bacterial acyltransferases of the SxxK superfamily vary enormously in sequence and function, with conservation of particular amino acid groups and all-α and α/β folds. They occur as independent entities (free-standing polypeptides) and as modules linked to other polypeptides (protein fusions). They can be classified into three groups. The group I SxxK d,d-acyltransferases are ubiquitous in the bacterial world. They invariably bear the motifs SxxK, SxN(D), and KT(S)G. Anchored in the plasma membrane with the bulk of the polypeptide chain exposed on the outer face of it, they are implicated in the synthesis of wall peptidoglycans of the most frequently encountered (4→3) type. They are inactivated by penicillin and other β-lactam antibiotics acting as suicide carbonyl donors in the form of penicillin-binding proteins (PBPs). They are components of a morphogenetic apparatus which, as a whole, controls multiple parameters such as shape and size and allows the bacterial cells to enlarge and duplicate their particular pattern. Class A PBP fusions comprise a glycosyltransferase module fused to an SxxK acyltransferase of class A. Class B PBP fusions comprise a linker, i.e., protein recognition, module fused to an SxxK acyltransferase of class B. They ensure the remodeling of the (4→3) peptidoglycans in a cell cycle-dependent manner. The free-standing PBPs hydrolyze d,d peptide bonds. The group II SxxK acyltransferases frequently have a partially modified bar code, but the SxxK motif is invariant. They react with penicillin in various ways and illustrate the great plasticity of the catalytic centers. The secreted free-standing PBPs, the serine β-lactamases, and the penicillin sensors of several penicillin sensory transducers help the d,d-acyltransferases of group I escape penicillin action. The group III SxxK acyltransferases are indistinguishable from the PBP fusion proteins of group I in motifs and membrane topology, but they resist penicillin. They are referred to as Penr protein fusions. Plausible hypotheses are put forward on the roles that the Penr protein fusions, acting as l,d-acyltransferases, may play in the (3→3) peptidoglycan-synthesizing molecular machines. Shifting the wall peptidoglycan from the (4→3) type to the (3→3) type could help Mycobacterium tuberculosis and Mycobacterium leprae survive by making them penicillin resistant