Gingipains are multi domain peptidases that are critical virulence factors expressed by the keystone periodontal disease pathogen P. gingivalis. The adhesion regions of these proteases are multi-domain complexes that are principally comprised of a number of modules that belong to the type 1 (T1) family of gingipain adhesins (also known as cleaved adhesin domains). We have previously reported the first crystal structures of three homologous variants of these 19 kDa T1 domains and shown that they recognise a number of host target proteins. We predicted from sequence analysis and binding data that in addition to the T1 domains the adhesion regions also contain a number of other unrelated adhesins (referred to here as type 2 or T2 gingpain adhesins) and synergistically contribute to the virulence of P. gingivalis. We have recombinantly expressed and crystallized the first example of an 17.5 kDA T2 adhesin coded for by a fragment of the gene for the lysine specific gingipain (kgp). We report here the structure refined at 1.05 angstroms resolution and thereby confirm the existence of the T2 domain family. This structure represents a new fold family which is distantly but only partially similar in topology to that of the plastocyanin/azurin family of proteins but with no copper binding sites. Like the T1 adhesins it contains a structural binding site for calcium. We observe that the recombinant T2 adhesin also binds directly to host target proteins but importantly can also inhibit bacterial invasion in cell based assays. The role of specific binding activity in the cell invasion mechanism conferred by T2 adhesins is likely to be a critical component the overall virulence of this pathogen.