BACKGROUND: [corrected] The Staphylococcus aureus collagen-binding protein Cna mediates bacterial adherence to collagen. The primary sequence of Cna has a non-repetitive collagen-binding A region, followed by the repetitive B region. The B region has one to four 23 kDa repeat units (B(1)-B(4)), depending on the strain of origin. The affinity of the A region for collagen is independent of the B region. However, the B repeat units have been suggested to serve as a 'stalk' that projects the A region from the bacterial surface and thus facilitate bacterial adherence to collagen. To understand the biological role of these B-region repeats we determined their three-dimensional structure. RESULTS: B(1) has two domains (D(1) and D(2)) placed side-by-side. D(1) and D(2) have similar secondary structure and exhibit a unique fold that resembles but is the inverse of the immunoglobulin-like (IgG-like) domains. Comparison with similar immunoglobulin superfamily (IgSF) structures shows novel packing arrangements between the D(1) and D(2) domains. In the B(1)B(2) crystal structure, an omission of a single glycine residue in the D(2)-D(3) linker loop, compared to the D(1)-D(2) and D(3)-D(4) linker loops, resulted in projection of the D(3) and D(4) in a spatially new orientation. We also present a model for B(1)B(2)B(3)B(4). CONCLUSIONS: The B region of the Cna collagen adhesin has a novel fold that is reminiscent of but is inverse in nature to the IgG fold. This B region assembly could effectively provide the needed flexibility and stability for presenting the ligand binding A region away from the bacterial cell surface.
BACKGROUND: [corrected] The Staphylococcus aureus collagen-binding protein Cna mediates bacterial adherence to collagen. The primary sequence of Cna has a non-repetitive collagen-binding A region, followed by the repetitive B region. The B region has one to four 23 kDa repeat units (B(1)-B(4)), depending on the strain of origin. The affinity of the A region for collagen is independent of the B region. However, the B repeat units have been suggested to serve as a 'stalk' that projects the A region from the bacterial surface and thus facilitate bacterial adherence to collagen. To understand the biological role of these B-region repeats we determined their three-dimensional structure. RESULTS: B(1) has two domains (D(1) and D(2)) placed side-by-side. D(1) and D(2) have similar secondary structure and exhibit a unique fold that resembles but is the inverse of the immunoglobulin-like (IgG-like) domains. Comparison with similar immunoglobulin superfamily (IgSF) structures shows novel packing arrangements between the D(1) and D(2) domains. In the B(1)B(2) crystal structure, an omission of a single glycine residue in the D(2)-D(3) linker loop, compared to the D(1)-D(2) and D(3)-D(4) linker loops, resulted in projection of the D(3) and D(4) in a spatially new orientation. We also present a model for B(1)B(2)B(3)B(4). CONCLUSIONS: The B region of the Cna collagen adhesin has a novel fold that is reminiscent of but is inverse in nature to the IgG fold. This B region assembly could effectively provide the needed flexibility and stability for presenting the ligand binding A region away from the bacterial cell surface.
Authors: Craig A McElroy; Paul J Holland; Peng Zhao; Jae-Min Lim; Lance Wells; Edward Eisenstein; Scott T R Walsh Journal: Proc Natl Acad Sci U S A Date: 2012-01-30 Impact factor: 11.205
Authors: Vengadesan Krishnan; Prabhat Dwivedi; Brandon J Kim; Alexandra Samal; Kevin Macon; Xin Ma; Arunima Mishra; Kelly S Doran; Hung Ton-That; Sthanam V L Narayana Journal: Acta Crystallogr D Biol Crystallogr Date: 2013-05-15
Authors: Paul G Young; Nicole J Moreland; Jacelyn M Loh; Anita Bell; Polly Atatoa Carr; Thomas Proft; Edward N Baker Journal: Infect Immun Date: 2014-04-28 Impact factor: 3.441