If one wants to better understand how plants grow, one must analyze the chemistry of life in its molecular detail. Michael Hothorn from the Friedrich-Miescher-Laboratory of the Max Planck Society in Tübingen and his team are doing just that.
Brassinosteroid receptor activation. (left panel) The steroid hormone brassinolide binds to a surface pocket of the BRI1 receptor (in blue). This creates a docking platform for the smaller and shape-complementary LRR-domain of SERK1 (in orange), which binds on top, with the steroid acting as a molecular glue (right panel).
Their latest work, published this week in Science, now reveals that a plant membrane receptor requires a helper protein to sense a growth-promoting steroid hormone and to transduce this signal across the cell membrane.
Every cell is surrounded by a greasy cell membrane. Signals from other cells and from the environment must be sensed at the cell surface, transduced across this membrane and translated into a specific response inside the cell. All organisms have evolved membrane receptor proteins to get these complex tasks done, but plant membrane receptors look drastically different from the well studied players in animals and bacteria. The plant steroid receptor BRI1, which can sense a small steroid hormone promoting plant growth, belongs to the family of leucine-rich repeat (LRR) receptor kinases, which are responsible for most membrane signaling events in plants.
It was previously shown that BRI1 directly binds the small steroid hormone with its LRR-domain at the cell surface. Julia Santiago, a postdoctoral fellow in the Hothorn lab, could now demonstrate that BRI1 requires a helper protein to correctly sense the hormone and transduce the signal across the membrane. The helper SERK1 is a known player in the brassinosteroid signaling pathway, but it came as a surprise to see how early on it is required. By hitting protein crystals containing the ternary BRI1 – steroid hormone – SERK1 complex with intense X-rays, Santiago could see that SERK1 contributes directly to the formation of the hormone binding pocket, with both proteins interacting with the hormone.
The steroid thus acts as a molecular glue which promotes association of the BRI1 and SERK1 LRR domains at the cell surface. This then causes interaction of the cytoplasmic kinases domains in the cell interior, which in turn activates a well characterized signaling pathway triggering the growth response.
The interesting feature of SERK1 is that it can help activate several seemingly unrelated plant receptor kinases, which bind vastly different ligands and trigger different responses. The new structures provide a first glimpse on how SERK1 might be able to do that. Instead of shaking hands with BRI1, it only uses a few 'finger tips' to contact the receptor. Other, strictly conserved surface patches remain available for the interaction with other plant receptor kinases and, potentially their ligands. “There must be some advantage to having all this different functions combined into a single helper protein”, Hothorn speculates. Notably, the use of a shared helper protein could allow different signaling pathway to communicate with each other.
The atomic models offer other novel insights too: “Looking at our models, we can now predict pretty well, which mutation in the receptor or helper protein should have an effect on the down-stream signaling pathway. We also know what parts of the hormone are really important to make it bind to the receptor or to the helper protein”. Such detailed insights may promote the rational design of synthetic plant steroid hormones and receptor antagonist with applications in basic research, and perhaps someday in the field.Resource:
Science Express August 9, 2013
Nadja Winter | Max-Planck-Institut
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy