Moraxella catarrhalisSynthesizes an Autotransporter That Is an Acid Phosphatase

Abstract

Moraxella catarrhalis O35E was shown to synthesize a 105-kDa protein that has similarity to both acid phosphatases and autotransporters. The N-terminal portion of the M. catarrhalis acid phosphatase A (MapA) was most similar (the BLAST probability score was 10 Initially thought to be a harmless commensal organism, Moraxella catarrhalis has gradually gained repute as an etiologic agent of at least two significant diseases in humans. This gram-negative, unencapsulated bacterium has been shown to colonize the upper airways of infants and very young children (14,15) and is one of the three most prominent causes of otitis media (45). Additionally, adults with chronic obstructive pulmonary disease are at risk for infectious exacerbations caused by M. catarrhalis (45,66). A recent study indicates that each year in the United States, as many as four million chronic obstructive pulmonary disease exacerbations may be attributed to M. catarrhalis (46).The secretion of proteins by gram-negative bacteria is a function necessary for numerous metabolic and physiologic processes. Five different secretion systems have been well characterized in bacteria (13), and a sixth has recently been described (44, 56). The type V secretion system has received increased attention in recent years (11,27,35,38). The absence of a requirement for energy coupling or accessory factors for successful protein secretion has resulted in this class of proteins being described as autotransporters. In gram-negative bacteria, autotransporters make up the largest family of outer membrane porins involved in protein translocation (12). The autotransporter secretion system was first described for the immunoglobulin A1 protease of Neisseria gonorrhoeae (54, 55), and subsequently, numerous autotransporters have been described for other gram-negative bacteria (25,27). A threedomain model for type V secretion systems has emerged, comprising (i) an amino-terminal leader peptide or signal sequence, (ii) the secreted mature protein (or passenger domain), and (iii) a C-terminal translocation domain responsible for the formation of a pore in the outer membrane to allow passage of the passenger domain to the cell surface (26).The passenger domains of previously described autotransporter systems have been shown to have widely different functions in gram-negative bacteria, including but not limited to proteolytic, adhesive, and cytotoxic activities (27). M. catarrhalis has been shown to synthesize at least three proteins (i.e., UspA1, UspA2, and Hag) that have been classified as trimeric autotransporters and one additional protein that is considered a conventional autotransporter (i.e., McaP) (for reviews, see references 11, 19, and 35). These four previously characterized M. catarrhalis autotransporters have been shown to be involved in adherence (1), serum resistance (6), binding of immunoglobulin D (18), autoaggregation (51), and lipolysis (68).Acid phosphatases catalyze the hydrolysis of phosphomonoesters at an acidic pH (9). Bacterial nonspecific acid phosphatases...

Characterization of a Unique Class C Acid Phosphatase from Clostridium perfringens

“…Multiple mechanisms are available to anchor a given polypeptide to a bacterial membrane. For example, Hoopman et al have demonstrated the existence of an acid phosphatase domain present as the N-terminal portion of the Moraxella catarrahlis MapA membrane-associated autotransporter protein (14). Irrespective of its anchoring mechanism, the preponderance of our data suggests CppA membrane association.…”

Use of the Chinchilla Model for Nasopharyngeal Colonization To Study Gene Expression by Moraxella catarrhalis

“…A DNA: DNA hybridization study was performed to determine the extent to which these ATCC 43617-derived probes would bind O35E-derived cDNAs. For this purpose, the O35E⌬mapA mutant (29) was used as a representative O35E-derived strain because this strain was a potential candidate for use in competitive index experiments in the chinchilla model. This O35E⌬mapA mutant differs from the O35E.118.rpsL strain only by the presence of a spectinomycin resistance cartridge inserted into its mapA gene (29) and the absence of the single nucleotide change in the rpsL gene.…”

“…For this purpose, the O35E⌬mapA mutant (29) was used as a representative O35E-derived strain because this strain was a potential candidate for use in competitive index experiments in the chinchilla model. This O35E⌬mapA mutant differs from the O35E.118.rpsL strain only by the presence of a spectinomycin resistance cartridge inserted into its mapA gene (29) and the absence of the single nucleotide change in the rpsL gene. When probed in DNA:DNA hybridization experiments with chromosomal DNA fragments from the homologous ATCC 43617 strain, a hybridization frequency of 99.1% was obtained.…”

Adhesion, Invasion, and Agglutination Mediated by Two Trimeric Autotransporters in the Human Uropathogen Proteus mirabilis

“…Translocator, or beta, domains of autotransporters are capable of transporting any heterologous passenger domain to the outer membrane (21,24). To determine if the C-terminal regions of AipA and TaaP function as true translocators, we translationally fused the regions corresponding to the beta domains of AipA (AipA ␤ ) and TaaP (TaaP ␤ ) individually to the passenger domain of Pta (Pta␣) (Fig.…”