Topography of ribosomes and initiation complexes from rat liver as revealed by atomic force microscopy

Atomic force microscopy (AFM) was used to image ribosomes and ribosomal subunits (60S, 40S and native 40S ribosomal subunits) isolated from rat liver. A variety of topographic images were obtained directly and found to be consistent with models established by other biophysical methods. In addition, the ternary complex of eIF-2 x GTP x Met-tRNA(i) and the 43S preinitiation complex have been discerned by AFM directly. Detailed information about the binding sites for eIF-1A, eIF-2, eIF-3, and Met-tRNA(i) on the 40S ribosomal subunit was derived from the AFM images. Finally, factors which may give rise to artifactual images, namely, convolution of the AFM tip on ribosomes, surface tension collapse effect and dehydration, are discussed. This work demonstrates that AFM is useful for imaging ribosomes and translational complexes and provides valuable information that can be used to complement other well-established techniques.