PBPlike

PBPlike refers to proteins that resemble penicillin-binding proteins (PBPs) but do not fit the classic definition of PBPs. The term is used in several studies to designate PBP-like domains found in predicted or annotated proteins where the canonical active-site motifs may be degenerate or absent, or where the overall architecture diverges from classical PBPs. These proteins are found in a broad range of bacteria and sometimes in mobile genetic elements, and they are often annotated as PBP-like in genome databases.

Structure and motifs: Most PBPlike proteins harbor a PBP-like transpeptidase fold, but many lack functional serine-based active sites such as SXXK, SXN, and KTG motifs, or possess altered residues that render them catalytically inactive. In some organisms, PBPlikes are fused to additional domains that mediate protein-protein interactions or cell wall remodeling.

Function: The precise roles of PBPlike proteins are diverse and context-dependent. In some cases they appear to act as structural adaptors or regulators of peptidoglycan synthesis, guiding cell wall remodeling without permanent enzymatic action. In others they may participate in signaling pathways, contribute to antibiotic tolerance, or have been co-opted in phage-related processes.

Discovery and study: PBPlike proteins are identified through genome sequencing and comparative genomics, with functional inference based on domain architecture and mutational analysis. Ongoing research seeks to clarify their contributions to cell envelope biogenesis and antibiotic response, as well as their potential as drug targets.