The emperor scorpion (Pandinus imperator) is not only one of the biggest scorpions in the world, but it also has one remarkably large protein, namely hemocyanin. Hemocyanin is a protein complex made up of 24 subunits that functions as blood pigment. It is one of the largest known proteins, comparable in size to ribosomes or even small viruses.
Hemocyanin of the emperor scorpion: model of the 24-meric protein complex and electron density at the active site where oxygen binding takes place.
Abb./©: E. Jaenicke et al (2012), PLoS One 7(3):e32548
For the first time ever, scientists from Johannes Gutenberg University Mainz in Germany have now successfully grown crystals from the emperor scorpion’s hemocyanin. With the help of x-rays, these crystals allow for a more precise analysis of the structure of the protein. Up to now, cryo-electron microscopy has primarily been used to examine large protein structures such as hemocyanin.This method has its disadvantages, however, because its resolution is not sufficient to be able to differentiate between single atoms. With x-ray crystallography, on the other hand, protein structure can be more precisely determined. It is even possible to determine the spatial arrangement of individual atoms. Scientists rely on this knowledge about the detailed molecular structure of these protein complexes in order to be able to understand how these proteins function.
For the first time ever, Professor Dr. Elmar Jaenicke from the Institute of Molecular Biophysics at Johannes Gutenberg University Mainz has managed to crystallize the blue hemocyanin protein complex from the emperor scorpion. This is the decisive first step toward successful x-ray structure determination because protein crystals are necessary to diffract x-rays so that the structure of the protein can be determined. Crystallization, however, is especially difficult for large protein complexes. "It is a little bit like a game of chance," Jaenicke describes the crystallization process, because the process is dependent on a number of factors such as the pH-level, the salinity of the solution, or the temperature. "The decisive step is always crystal nucleation," which, according to Jaenicke, can take months and requires a lot of patience. Sometimes, it even takes several years to optimize the conditions for crystallization. This is the reason why so far only a handful of molecular structures of very large protein complexes have been solved using x-ray structure determination worldwide. In fact, one of these structural analyses – namely that of the ribosome – was awarded the Nobel Prize in 2009.
The crystals are measured in the x-ray beam, and the structure is then determined through complex calculations based on the scattered x-rays. At first, Jaenicke and his team of scientists were able to attain a mid-resolution (6.5 ångströms) structure for the emperor scorpion's protein with which secondary structures such as α-helices could be seen, but other elements, such as single amino acids, could not yet be ascertained. In layman's terms: If the protein is a brick house and a telescope is used to try to look at its structure from far away, the windows, doors, and the mailbox would be visible at the current resolution, but the arrangement of the individual bricks would not. "This was our starting point and now we can already see parts of the active site of the molecule. With further improvements to our crystals, we are well on our way to achieving an atomic resolution that is not possible with any other method." According to Jaenicke, the oxygen binding protein from the emperor scorpion would then be one of the five largest structures to have been deciphered using x-ray structure analysis to date.
Johannes Gutenberg University Mainz has the ideal infrastructure to support this type of structural research on very large protein complexes which can only be done at a few research institutes around the world. In Mainz, x-ray structure determination projects in the research groups of Professor Dr. Heinz Decker and Professor Dr. Elmar Jaenicke at the Institute of Molecular Biophysics cover the atomic resolution range, cryo-electron microscopy studies in the research group of Professor Dr. Jürgen Markl at the Institute of Zoology take care of the mid-resolution range. The new rotating anode x-ray generator used at the Institute of Molecular Biophysics is also ideal for determination of the structure of these giant molecules because it produces focused x-ray beams with an intensity comparable to that of second-generation synchrotron beamlines.
Petra Giegerich | idw
Further reports about: > Biophysics > Molecular Biophysics > Molecular Target > amino acid > atomic resolution > blood protein > cryo-electron microscopy > electron microscopy > hemocyanin > molecular structure > molecular switch > protein complexes > protein structure > single atom > very large protein complexes
Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute
Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy