Chemical derivatization of peptide carboxyl groups for highly efficient electron transfer dissociation.

The carboxyl groups of tryptic peptides were derivatized with a tertiary or quaternary amine labeling reagent to generate more highly charged peptide ions that fragment efficiently by electron transfer dissociation (ETD). All peptide carboxyl groups-aspartic and glutamic acid side-chains as well as C-termini-were derivatized with an average reaction efficiency of 99 %. This nearly complete labeling avoids making complex peptide mixtures even more complex because of partially-labeled products, and it allows the use of static modifications during database searching.

IpaA targets beta1 integrins and rho to promote actin cytoskeleton rearrangements necessary for Shigella entry.

Shigella invasion into the colonic epithelium involves many steps including the formation of large membrane protrusions by the epithelial cells that facilitate bacterial engulfment. IpaA, a Shigella protein secreted into target cells upon cell contact induces a loss of actin stress fibers in cells and promotes the reorganization of actin at the site of entry. The mechanism for this is not known but is thought to involve recruitment of the focal adhesion protein vinculin to IpaA.