K2 capsular polysaccharide degradation by a bacteriophage depolymerase does not require trimer formation.
Journal
mBio
Journal Volume
15
Journal Issue
3
ISSN
2150-7511
Date Issued
2024-03-13
Author(s)
Ye, Ting-Juan
Fung, Kit-Man
Lee, I-Ming
Ko, Tzu-Ping
Lin, Chia-Yi
Wong, Chia-Ling
Tu, I-Fan
Huang, Tzu-Yin
Yang, Feng-Ling
Chang, Yu-Pei
Lin, Tzu-Lung
Huang, Kai-Fa
Wu, Shih-Hsiung
Abstract
K2-capsular Klebsiella pneumoniae is a hypervirulent pathogen that causes fatal infections. Here, we describe a phage tailspike protein, named K2-2, that specifically depolymerizes the K2 capsular polysaccharide (CPS) of K. pneumoniae into tetrasaccharide repeating units. Nearly half of the products contained O-acetylation, which was thought crucial to the immunogenicity of CPS. The product-bound structures of this trimeric enzyme revealed intersubunit carbohydrate-binding grooves, each accommodating three tetrasaccharide units of K2 CPS. The catalytic residues and the key interactions responsible for K2 CPS recognition were identified and verified by site-directed mutagenesis. Further biophysical and functional characterization, along with the structure of a tetrameric form of K2-2, demonstrated that the formation of intersubunit catalytic center does not require trimerization, which could be nearly completely disrupted by a single-residue mutation in the C-terminal domain. Our findings regarding the assembly and catalysis of K2-2 provide cues for the development of glycoconjugate vaccines against K. pneumoniae infection.
Subjects
Klebsiella pneumonia
O-acetylation
bacteriophage
intersubunit carbohydrate-binding site
tailspike protein
SDGs
Type
journal article