13 research outputs found
Substrate Recognition of PLCÎł1 via a Specific Docking Surface on Itk
Itk (interleukin-2 inducible T cell kinase) is a non-receptor protein tyrosine kinase expressed primarily in T cells. Itk catalyzes phosphorylation on tyrosine residues within a number of its natural substrates, including the well-characterized Y783 of PLCÎł1. However, the molecular mechanisms Itk exploits to recognize its substrates are not completely understood. We have previously identified a specific docking interaction between the kinase domain of Itk and the C-terminal Src homology 2 (SH2C) domain of PLCÎł1 that promotes substrate specificity for this enzyme/substrate pair. In the current study, we identify and map the interaction surface on the Itk kinase domain as an acidic patch centered on the G helix. Mutation of the residues on and adjacent to the G helix within the Itk kinase domain impairs the catalytic efficacy of PLCÎł1 substrate phosphorylation by specifically altering the proteinâprotein interaction interface and not the inherent catalytic activity of Itk. NMR titration experiments using a Btk (Brutonâs tyrosine kinase) kinase domain as a surrogate for the Itk kinase domain provide further support for an Itk/PLCÎł1 SH2C interaction surrounding the G helix of the kinase domain. The work presented here provides structural insight into how the Itk kinase uses the G helix to single out Y783 of PLCÎł1 for specific phosphorylation. Comparing these results to other well-characterized kinase/substrate systems suggests that the G helix is a general structural feature used by kinases for substrate recognition during signaling. [Figure: see text
Time Resolved Measurements of Speciated Tailpipe Emissions from Motor Vehicles: Trends with Emission Control Technology, Cold Start Effects, and Speciation
Experiments
were conducted at the California Air Resources Board
Haagen-Smit Laboratory to understand changes in vehicle emissions
in response to stricter emissions standards over the past 25 years.
Measurements included a wide range of volatile organic compounds (VOCs)
for a wide range of spark ignition gasoline vehicles meeting varying
levels of emissions standards, including all certifications from Tier
0 up to Partial Zero Emission Vehicle. Standard gas chromatography
(GC) and high performance liquid chromatography (HLPC) analyses were
employed for drive-cycle phase emissions. A proton-transfer-reaction
mass spectrometer measured time-resolved emissions for a wide range
of VOCs. Cold-start emissions occur almost entirely in the first 30â60
s for newer vehicles. Cold-start emissions have compositions that
are not significantly different across all vehicles tested and are
markedly different from neat fuel. Hot-stabilized emissions have varying
importance depending on species and may require a driving distance
of 200 miles to equal the emissions from a single cold start. Average
commute distances in the U.S. suggest the majority of in-use vehicles
have emissions dominated by cold starts. The distribution of vehicle
ages in the U.S. suggests that within several years only a few percent
of vehicles will have significant driving emissions compared to cold-start
emissions
New Guinea has the worldâs richest island flora
New Guinea is the worldâs largest tropical island and has fascinated naturalists for centuries1,2. Home to some of the best-preserved ecosystems on the planet3 and to intact ecological gradientsâfrom mangroves to tropical alpine grasslandsâthat are unmatched in the Asia-Pacific region4,5, it is a globally recognized centre of biological and cultural diversity6,7. So far, however, there has been no attempt to critically catalogue the entire vascular plant diversity of New Guinea. Here we present the first, to our knowledge, expert-verified checklist of the vascular plants of mainland New Guinea and surrounding islands. Our publicly available checklist includes 13,634 species (68% endemic), 1,742 genera and 264 familiesâsuggesting that New Guinea is the most floristically diverse island in the world. Expert knowledge is essential for building checklists in the digital era: reliance on online taxonomic resources alone would have inflated species counts by 22%. Species discovery shows no sign of levelling off, and we discuss steps to accelerate botanical research in the âLast Unknownâ8