these OMP profiles with monoclonal antibodies (MAbs) revealed that a few proteins with similar molecular masses in the different strains have cross-reactive epitopes. Also, a surface-exposed protein on M. catarrhalis has an unusually high molecular mass. An 80-kDa OMP on M. catarrhalis is immunogenic and common to all nonencapsulated strands of M. catarrhalis, which suggests it may be used as an antigen for immunization. Protein secretion Moraxella catarrhalis utilizes the twin-arginine translocation pathway (TAT pathway) for the transport of folded proteins across the inner membrane. The translocase apparatus is a typical Gram-negative TAT translocase consisting of three essential membrane proteins: TatA, TatB and TatC. TatA proteins form a pore through which passenger proteins are transported and TatB and TatC proteins recognize, bind and direct the passenger proteins to the membrane spanning TatA pore. The M. catarrhalis TAT translocase protein encoding genes tatA, tatB and tatC are located in a single tatABC locus in the bacterial chromosome and are likely to be transcriptionally and translationally linked due to a single-nucleotide overlap between each gene. Multiple M. catarrhalis proteins have been predicted or tested to contain the highly conserved leader motif for translocation and to be transported by the TAT pathway. Beta-lactamases BRO-1 and BRO-2 have been shown to be transported by the TAT pathway. Other potential passenger proteins include an iron-dependent peroxidase -like protein, a cytochrome c -like protein and a phosphate ABC transporter inner membrane protein- like protein. A functioning TAT pathway is necessary for the optimal growth of M. catarrhalis even in conditions without antibiotics. References External links Type strain of Moraxella catarrhalis at BacDive – the Bacterial Diversity Metadatabase Moraxellaceae