Expanding the substrate tolerance of biotin ligase through exploration of enzymes from diverse species

Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Journal of the American Chemical Society (Impact Factor: 11.44). 02/2008; 130(4):1160-2. DOI: 10.1021/ja076655i
Source: PubMed

ABSTRACT Technologies that enable the site-specific conjugation of chemical probes onto proteins are extremely useful for applications in cell biology and proteomics. We cloned, expressed, and purified biotin ligases from nine different species and screened them for the ability to ligate unnatural analogues of biotin onto the human p67 biotin acceptor domain. We discovered that the biotin ligases of Saccharomyces cerevisiae (yeast) and Pyrococcus horikoshii could accept alkyne and azide derivatives of biotin, respectively. HPLC, gel-shift, and mass spectrometry assays confirmed that these ligation reactions were ATP-and enzyme-dependent, as well as site-specific. We used the P. horikoshii-catalyzed azide ligation reaction to site-specifically introduce a phosphine probe onto p67 using the Staudinger ligation. These new ligation reactions demonstrate the differential substrate specificities of biotin ligases from different organisms and open the door to novel protein labeling applications.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: G protein-coupled receptors (GPCRs) are targets for a quarter of prescription drugs. Despite recent progress in structural biology of GPCRs, only few key conformational states in the signal transduction process have been elucidated. Agonist ligands frequently display functional selectivity where activated receptors are biased to either G protein- or arrestin-mediated downstream signaling pathways. Selective manipulation of individual steps in the GPCR activation scheme requires precise information about the kinetics of ligand binding and the dynamics of downstream signaling. One approach is to obtain time-resolved information using receptors tagged with fluorescent or structural probes. Recent advances allow for site-specific introduction of genetically encoded unnatural amino acids into expressed GPCRs. We describe how bioorthogonal functional groups on GPCRs enable the mapping of receptor-ligand interactions and how bioorthogonal chemical reactions can be used to introduce fluorescent labels for single-molecule fluorescence applications to study the kinetics and conformational dynamics of GPCR signaling complexes ("signalosomes").
    Chemistry & Biology 09/2014; 21(9):1224-1237. DOI:10.1016/j.chembiol.2014.08.009 · 6.59 Impact Factor
  • Chemical Reviews 03/2014; 114(9). DOI:10.1021/cr400355w · 45.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Fluorescence methods allow one to monitor protein conformational changes, protein-protein associations, and proteolysis in real time, at the single molecule level and in living cells. The information gained in such experiments is a function of the spectroscopic techniques used and the strategic placement of fluorophore labels within the protein structure. There is often a trade-off between size and utility for fluorophores, whereby large size can be disruptive to the protein's fold or function, but valuable characteristics, such as visible wavelength absorption and emission or brightness, require sizable chromophores. Three major types of fluorophore readouts are commonly used: (1) Forster resonance energy transfer (FRET); (2) photoinduced electron transfer (PET); and (3) environmental sensitivity. This review focuses on those probes small enough to be incorporated into proteins during ribosomal translation, which allows the probes to be placed on the interiors of proteins as they are folded during synthesis. The most broadly useful method for doing so is site-specific unnatural amino acid (UAA) mutagenesis. We discuss the use of UAA probes in applications relying on FRET, PET, and environmental sensitivity. We also briefly review other methods of protein labelling and compare their relative merits to UAA mutagenesis. Finally, we discuss small probes that have thus far been used only in synthetic peptides, but which have unusual value and may be candidates for incorporation using UAA methods.
    Australian Journal of Chemistry 01/2014; 67(5):686. DOI:10.1071/CH13554 · 1.64 Impact Factor

Full-text (2 Sources)

Available from
May 28, 2014