Structure aided design of a Neu5Gc specific lectin.

ABSTRACT: Subtilase cytotoxin (SubAB) of Escherichia coli is an AB5 class bacterial toxin. The pentameric B subunit (SubB) binds the cellular carbohydrate receptor, ?2-3-linked N-glycolylneuraminic acid (Neu5Gc). Neu5Gc is not expressed on normal human cells, but is expressed by cancer cells. Elevated Neu5Gc has been observed in breast, ovarian, prostate, colon and lung cancer. The presence of Neu5Gc is prognostically important, and correlates with invasiveness, metastasis and tumour grade. Neu5Gc binding by SubB suggests that it may have utility as a diagnostic tool for the detection Neu5Gc tumor antigens. Native SubB has 20-fold less binding to N-acetlylneuraminic acid (Neu5Ac); over 30-fold less if the Neu5Gc linkage was changed from ?2-3 to ?2-6. Using molecular modeling approaches, site directed mutations were made to reduce the ?2-3?[Formula: see text]??2-6-linkage preference, while maintaining or enhancing the selectivity of SubB for Neu5Gc over Neu5Ac. Surface plasmon resonance and glycan array analysis showed that the SubB?S106/?T107 mutant displayed improved specificity towards Neu5Gc and bound to ?2-6-linked Neu5Gc. SubB?S106/?T107 could discriminate NeuGc- over Neu5Ac-glycoconjugates in ELISA. These data suggest that improved SubB mutants offer a new tool for the testing of biological samples, particularly serum and other fluids from individuals with cancer or suspected of having cancer.

SUBMITTER: Day CJ 

PROVIDER: S-EPMC5431456 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature