Inhibits cell wall synthesis by binding to lipid II, which is used as a precursor to peptidoglycan. Without a peptidoglycan layer, bacteria become vulnerable to lysis.
Teixobactin also binds to lipid III, which acts as a precursor to teichoic acid. This is what gives the cell wall its rigidity to resist degradation by autolysins. Without this, the bacteria becomes vulnerable to lysis.
It binds to multiple enzymatic substrates rather than to an enzyme. It is much harder for resistance to build, as mutating the substrate for an enzymatic reaction is much more difficult for an organism than simply mutating amino acids to change the enzyme.
CURRENT KNOWLEDGE OF MECHANISM
Of all of the targets of teixobactin, none are proteins. This makes it more difficult for mutations that would develop mutations to occur - the targets are key parts of the bacterial structure.
Teixobactin was showed to inhibit peptidoglycan synthesis but was not incorporated in DNA, RNA, or other proteins. This also adds to the promise of little resistance conferring.
It starts as a ClpP protease that is converted into a non-specific hydrolase. By binding competitively to a teichoic acid precursor, it inhibits cell wall generation and ultimately kills the cell with liberated autolysins.