Imaging glucoamylase by scanning tunnelling microscopy

Abstract

Images of the enzymes glucoamylase 1 and glucoamylase 2 and G1C (a proteolytically derived C-terminal fragment of glucoamylase 1) have been obtained by scanning tunnelling microscopy (STM). The images of glucoamylase 2 and G1C show that these proteins are nearly spherical globular proteins. In contrast, images of glucoamylase 1 show that it is a dumb-bell shaped globular protein. Problems encountered in (i) imaging these proteins and (ii) validating and interpreting the images obtained by STM are discussed.