SpaB, an atypically adhesive basal pilin from the lactobacillar SpaCBA pilus: crystallization and X-ray diffraction analysis

Microbial attachment to host surfaces is a critical step in colonization. Hence, interfering with the initial attachment is considered as one of the attractive and efficient approaches in improving health and combating infections. Towards providing the essential foundations for this approach, Dr Krishnan’s structural biology group currently focus on hair-like surface organelles called pili or fimbriae that enable bacteria to establish the initial contacts with the host surfaces for colonization and biofilm formation. As part of their on-going structural investigation programme, the group has previously determined the structure of three building blocks (SpaA, SpaD and SpaE) of pili from a gut-adapted Lactobacillus rhamnosus GG, and proposed a mechanism called ‘expose-ligate-seal’ for pilus shaft formation and basal pilin incorporation (J. Struct. Biol. 207:74, 2019; Comm. Biol. 1:94, 2018; Sci. Rep. 6:28664, 2016). The group has recently crystallized a basal block (SpaB) which anchors the assembled pili on the bacterial cell surface with the help of sortase enzyme. Crystallization of SpaB remained particularly challenging until the implementation of a three-pronged crystallization approach involving C-terminal tail truncation, surface lysine methylation and magnesium additives. Their on-going structure determination work will provide insights about pilus anchoring and attachment.

For details:

• SpaB, an atypically adhesive basal pilin from the lactobacillar SpaCBA pilus: crystallization and X-ray diffraction analysis.
• https://scripts.iucr.org/cgi-bin/paper?rl5181
• https://twitter.com/ActaCrystF/status/1197318728410636289?s=19