The annexin A3-membrane interaction is modulated by an N-terminal tryptophan.

The crystal structure of annexin A3 (human annexin III) solved recently revealed a well-ordered folding of its N-terminus with the side chain of tryptophan 5 interacting with residues at the extremity of the central pore. Since the pore of annexins has been suggested as the ion pathway involved in membrane permeabilization by these proteins, we investigated the effect of the N-terminal tryptophan on the channel activity of annexin A3 by a comparative study of the wild-type and the W5A mutant in structural and functional aspects. Calcium influx and patch-clamp recordings revealed that the mutant exhibited an enhanced membrane permeabilization activity as compared to the wild-type protein.

The high-resolution crystal structure of human annexin III shows subtle differences with annexin V.

The structure of recombinant human annexin III was solved to 1.8 A resolution. Though homologous to annexin I and V, the annexin III structure shows significant differences.