Nanotechnology is the logical consequence of miniaturization and it presents new technology opportunities and manufacturing challenges. Protein structures can help to address the nano-manufacturing problems. A class of proteins known as chaperonins can be restructured by methods of genetic engineering to produce designer proteins which function as nano-scale templates.

Jonathan Trent and coworkers at NASA Ames Research Center have been studying "heat shock protein 60" (HSP60) in organisms living at high temperatures, the so-called "thermophiles." Their work is primarily focused on using nanobiotech methods to create enzyme arrays for biofuels production. The HSP60 can be purified from cells of S. shibatae as a double-ring structure consisting of 16-18 subunits. The latest publication of the group outlines some of the work done with modified proteins.

	Ribbon diagram of subunits and single rings with exposed α-helices.

 Abstract

Much effort has gone into finding peptides that bind potentially useful nanoparticles, but relatively little effort has focused on the scaffolds that organize these peptides into useful nanostructures. Chaperonins are protein complexes with 14-18 protein subunits that self-assemble into double-ring complexes and function as scaffolds for peptides or amino acids that bind metallic and semiconductor quantum dots. The utility of chaperonins as scaffolds depends on their structure and their ability to self-assemble into double-rings and higher-order structures, such as filaments and two-dimensional arrays. To better understand the structure of chaperonins, we constructed a model of a group II chaperonin and, based on this model, genetically constructed five mutant subunits with significant deletions. We expressed these mutants as recombinant proteins and observed by native polyacrylamide gel electrophoresis (PAGE) and transmission electron microscopy (TEM) that they all self-assembled into double rings. Our model predicted and TEM confirmed that these deletions did not significantly change the 17 nm diameter of the wild-type double rings, but decreased their height and opened their central cavities. Four of the five mutants formed higher-order structures: chains of rings, bundles of chains or filaments, and two-dimensional arrays, which we suggest can be useful nanostructures.

Source: Mutant chaperonin proteins: new tools for Nanotechnology, Li1, Y., Paavola, C.D., Kagawa1, H., Chan, S.L., Trent, J.D; Nanotechnology 18 (2007) 000000.

Queries for IOP paper 254606