This domain is found towards the C-terminal of adhesins from Mycoplasmas, such as adhesin P1, first identified as the major determinant for cytoadherence and gliding motility in M. pneumoniae. P1 forms a transmembrane adhesion complex with P40/P90, called 'Nap', which mediates motility and infectivity in these organisms. The C-terminal domain is smaller than the large N-terminal domain and is mostly conserved [1,2]. It is followed by a transmembrane domain and acts as a stalk connecting the large N-terminal domain with the outer surface of the cell membranes [2,3]. P1 N-terminal domain is highly variable (Pfam:PF12378).

1: Sequence analysis of 56 kb from the genome of the bacterium Mycoplasma pneumoniae comprising the dnaA region, the atp operon and a cluster of ribosomal protein genes. Hilbert H, Himmelreich R, Plagens H, Herrmann R; Nucleic Acids Res 1996;24:628-639. PMID:8604303

2: Immunodominant proteins P1 and P40/P90 from human pathogen Mycoplasma pneumoniae. Vizarraga D, Kawamoto A, Matsumoto U, Illanes R, Perez-Luque R, Martin J, Mazzolini R, Bierge P, Pich OQ, Espasa M, Sanfeliu I, Esperalba J, Fernandez-Huerta M, Scheffer MP, Pinyol J, Frangakis AS, Lluch-Senar M, Mori S, Shibayama K, Kenri T, Kato T, Namba K, Fita I, Miyata M, Aparicio D; Nat Commun. 2020;11:5188. PMID:33057023

3: Structure and mechanism of the Nap adhesion complex from the human pathogen Mycoplasma genitalium. Aparicio D, Scheffer MP, Marcos-Silva M, Vizarraga D, Sprankel L, Ratera M, Weber MS, Seybert A, Torres-Puig S, Gonzalez-Gonzalez L, Reitz J, Querol E, Pinol J, Pich OQ, Fita I, Frangakis AS; Nat Commun. 2020;11:2877. PMID:32513917