Molecular engineering

Monoclonal antibodies without screening

In developing a pipeline for rapid monoclonal antibody production, Reddy et al. describe a strategy that bypasses the need for extensive screening of immortalized B cells or recombinant antibody libraries. Instead, they used high-throughput DNA sequencing to identify the variable region gene repertoires produced by bone marrow plasma cells of immunized mice. They paired the most abundant variable region heavy and light chain genes, reconstructed them using automated gene synthesis and recombinantly expressed the monoclonal antibodies.

Reddy, S.T. et al. Nat. Biotechnol. 28, 965–969 (2010).

Imaging

Imaging mRNA transport

It is challenging to clearly observe mRNA export from nuclear pores. Grünwald and Singer now describe a super-registration approach for fluorescence microscopy that facilitates measuring distances between different fluorophores with very high time and spatial precision. This technique allowed them to observe the kinetics of β-actin mRNA transport in mammalian cells with an order of magnitude greater precision than previously possible. The method should be useful for imaging other transient cellular processes.

Grünwald, D. & Singer, R.H. Nature 467, 604–607 (2010).

Epigenetics

Mapping the histone methyl lysine interactome

Vermeulen et al. report an integrated approach to understand how histone methyl lysine modifications regulate gene expression. First, they used quantitative mass spectrometry to identify proteins that bound to trimethyl lysine marks on histones H3 and H4. Then they fluoroscently tagged the identified proteins and performed pulldowns to identify physical interactions. Finally, using chromatin immunoprecipitation and DNA sequencing, they identified the genomic binding sites of the proteins. The resulting dataset is a rich resource for chromatin researchers.

Vermeulen, M. et al. Cell 142, 967–980 (2010).

Bioinformatics

Enzyme discovery without evolution

Before embarking on extensive direct evolution experiments to create enzymes with new activities, it is worth checking first whether such tools already exist in nature. Höhne et al. show that enzymes can be discovered by using rational design principles to predict key amino acids that perform the desired activity and then searching protein sequence databases to find proteins that already have these sequences. Applying this approach, they identified 17 (R)-enantioselective amine transaminases.

Höhne, M. et al. Nat. Chem. Biol. 6, 807–813 (2010).

Biophysics

Monitoring membrane protein interactions

Casuso et al. show that high-speed atomic force microscopy (HS-AFM) can be used to experimentally monitor bacteriorhodopsin dynamics in native purple membranes from Halobacterium salinarum. Whereas AFM has a typical image scanning speed of about one minute, HS-AFM can record an image in about 187 milliseconds, allowing them to observe the movement of ATP-synthase c-rings, undetectable by other methods.

Casuso, I. et al. Biophys. J. 99, L47–L49 (2010).