6POO

Novel structure of the N-terminal helical domain of BibA, a group B streptococcus immunogenic bacterial adhesin

Summary for 6POO

• Entry DOI: 10.2210/pdb6poo/pdb
• Descriptor: BibA (1 entity in total)
• Functional Keywords: biba, immunogenic, bacteria, adhesin, group b streptococcus, immune system
• Biological source: Streptococcus agalactiae
• Total number of polymer chains: 1
• Total formula weight: 30970.52

Authors

Manne, K.,Narayana, S.V. (deposition date: 2019-07-04, release date: 2020-08-12, Last modification date: 2024-10-23)

Primary citation

Manne, K.,Chattopadhyay, D.,Agarwal, V.,Blom, A.M.,Khare, B.,Chakravarthy, S.,Chang, C.,Ton-That, H.,Narayana, S.V.L.
Novel structure of the N-terminal helical domain of BibA, a group B streptococcus immunogenic bacterial adhesin.
Acta Crystallogr D Struct Biol, 76:759-770, 2020

PubMed Abstract: BibA, a group B streptococcus (GBS) surface protein, has been shown to protect the pathogen from phagocytic killing by sequestering a complement inhibitor: C4b-binding protein (C4BP). Here, the X-ray crystallographic structure of a GBS BibA fragment (BibA) and a low-resolution small-angle X-ray scattering (SAXS) structure of the full-length N-terminal domain (BibA) are described. The BibA fragment crystal structure displayed a novel and predominantly helical structure. The tertiary arrangement of helices forms four antiparallel three-helix-bundle-motif repeats, with one long helix from a bundle extending into the next. Multiple mutations on recombinant BibA delayed the degradation of the protein, and circular dichroism spectroscopy of BibA suggested a similar secondary-structure composition to that observed in the crystallized BibA fragment. A model was generated for the 92 N-terminal residues (BibA) using structural similarity prediction programs, and a BibA model was generated by combining the coordinates of BibA and BibA. The X-ray structure of BibA and the model of BibA fitted well into the calculated SAXS envelope. One possible binding site for the BibA N-terminal domain was localized to the N-terminal CCP (complement-control protein) domains of the C4BP α-chain, as indicated by the decreased binding of BibA to a ΔCCP1 C4BP α-chain mutant. In summary, it is suggested that the GBS surface protein BibA, which consists of three antiparallel α-helical-bundle motifs, is unique and belongs to a new class of Gram-positive surface adhesins.

PubMed: 32744258
DOI: 10.1107/S2059798320008116

Experimental method

X-RAY DIFFRACTION (3.03 Å)