Proteins as Parents

So that we can move, and so that our heart beats, we need proteins with special mechanical properties, "molecular springs", which give our tissues the necessary strength and take care of elasticity and tensibility.

Such proteins are also interesting as building blocks for novel high-tech materials because the natural materials often outperform the artificial: One only has to think about the highly elastic and extremely tear-proof spider dragline silk. Molecules with defined mechanical properties are especially needed for the assembly of nanotechnological devices. A team from the University of British Columbia (Vancouver, Canada) succeeded in producing proteins with new mechanical properties through the combination of two "parent" protein fragments.

The research group of Hongbin Li chose two different titin domains from heart muscle for their experiments. Titin, a giant molecule, is responsible for controlling the passive tension of our muscles and also pulls them together again after an extension. Depending on the type of muscle, there are differences: The titin found in heart muscle is less tensile than that found in skeletal muscle and it gives the heart the necessary stability to resist the pressure of the inflowing blood.

As the parent generation, the scientists chose two globular titin domains called I27 and I32, whose mechanical properties have already been intensively researched. Both are similarly built and are composed of the protein segments A, A’, as well as B to G. The researchers interchanged several fragments of the genes that encode I27 and I32 ("DNA shuffling"). Genetically they produced four different protein "children": an I27 with the A’/G strands from I32, an I32 with A’/G from I27, an I27 with C, D, and E from I32, and also an I32 with the C, D, and E strands from I27.

The mechanical properties of all the proteins were investigated with atomic force microscopy. To do this, one end of the protein chain was attached onto a solid support and the other end was adsorbed onto the tip of the atomic force microscope. When the tip is gradually pulled away from the support, the protein elongates and the force increases until the protein finally unfolds. The resultant force–extension curves characterize the mechanical properties of the proteins. It turned out that all children show different mechanical characteristics to their parents. It was previously thought that the specific arrangement of the A’/G section was critical for the mechanical stability of the domain, whereas other parts of the domain, including the C, D, and E strands, only played a less- significant role. This opinion must now be revised.

Li hopes that this exciting new application of the powerful recombination technique in the field of protein mechanics will open a new way to tailor proteins’ mechanical properties.

Citation: Hongbin Li, Engineering Proteins with Novel Mechanical Properties by Recombination of Protein Fragments, Angewandte Chemie International Edition 2006, 45, No. 34, doi: 10.1002/anie.200600382

Source: Angewandte Chemie

Related stories:

The search for 'green' gold in the Amazon rain forest
(PhysOrg.com) -- In a hunt for plants in the Amazon rain forest that have potential to be used for sustainable light-weight construction beams, electronic cases or other high-performance materials, Cornell fiber science professors Anil Netravali and Juan Hinestroza are forging new collaborations with researchers in Brazil.
Gold, DNA Combination May Lead To Nano-Sensor
The ability to use genetic material to assemble nanoscopic particles of gold could be an important step toward creating tiny “spies” that will be able to infiltrate individual cells and report back in real time on the cell’s inner workings.
Nanotubes could help study retrovirus transmission between human cells
Recent findings by medical researchers indicate that naturally occurring nanotubes may serve as tunnels that protect retroviruses and bacteria in transit from diseased to healthy cells — a fact that may explain why vaccines fare poorly against some invaders.
Nanotubes could aid understanding of retrovirus transmission between human cells
Recent findings by medical researchers indicate that naturally occurring nanotubes may serve as tunnels that protect retroviruses and bacteria in transit from diseased to healthy cells — a fact that may explain why vaccines fare poorly against some invaders.

Stretchy spider silks can be springs or rubber
It’s stronger than steel and nylon, and more extensible than Kevlar. So what is this super-tough material? Spider silk; and learning how to spin it is one of the materials industries’ Holy Grails. John Gosline has been fascinated by spider silks and their remarkable toughness for most of his scientific career.
Protein Fibrils as Alternative Plastics?
Amyloid deposits in tissues and organs are linked to a number of diseases, including Alzheimer’s, Parkinson’s, type II diabetes, and prion diseases such as BSE. However, amyloids are not just pathological substances; they have potential as a nanomaterials.
Engineers 'bone' up on biological materials
In a recent feature article published in Materials Research Society's Bulletin, Dr Michelle Oyen explores the potential uses of synthetic bone-like material. Michelle suggests that these materials will be too expensive to replace materials in typical construction and building applications but can be developed for use in particularly demanding sections of advanced architecture as well as other specialist structural applications.
Researchers unveil a new class of fatty acids
CSIRO researchers have discovered a new class of fatty acids – alpha-hydroxy polyacetylenic fatty acids – that could be used as sensors for detecting changes in temperature and mechanical stress loads.

News discussion:

General Science news