Crystallin proteins

B. thurigiensis is a common Gram-positive, spore-forming soil bacterium that produces inclusion bodies, microcrystalline clusters of many different proteins. These crystalline proteins, called 5-endotoxins, are the ion channel toxins that are sold commercially for pest control. Most such endotoxins are protoxins, which are inactive until cleaved to smaller, active proteins by proteases in the gut of a susceptible insect. One such crystalline protoxin. 

With certain Lepidoptera, the crystalline protein alone is not sufficiently toxic to cause a quick kill, and the normal course of tissue invasion by viable bacilli must take place to kill the host. Indeed, this is probably required for the bulk of susceptible Lepidoptera. However, the ability of crystal alone to produce kill (and similar singular action of another toxin produced by these bacilli on flies) places the compounds within the realm of true toxicants and mandates their consideration as chemical entities. 

The bacterial culture converts a portion of the supplied nutrient into vegetative cells, spores, crystalline protein toxin, soluble toxins, exoenzymes, and metabolic excretion products by the time of complete sporulation of the population. Although synchronous growth is not necessary, nearly simultaneous sporulation of the entire population is desired in order to obtain a uniform product. Depending on the manner of recovery of active material for the product, it will contain the insolubles including bacterial spores, crystals, cellular debris, and residual medium ingredients plus any soluble materials which may be carried with the fluid constituents. Diluents, vehicles, stickers, and chemical protectants, as the individual formulation procedure may dictate, are then added to the harvested fermentation products. The materials are used experimentally and commercially as dusts, wettable powders, and sprayable liquid formulations. Thus, a... 

Materials produced by crystalliferous bacilli which elicit a toxic response in susceptible insects may be separated into two types. The first type, the true toxins, include the crystalline protein inclusion body the parasporal body of Hannay (14)], a heat-stable, water-soluble exotoxin active against flies, a heat-stable, dialyzable water-soluble exotoxin, toxic to Lepidoptera on injection (23), and a heat-labile, water-soluble, filterable exotoxin, toxic toward larch sawfly larvae (Hymenoptera) which was reported by Smirnoff (31). 

Morris DR, LP Hager (1966) Chloroperoxidase 1 Isolation and properties of the crystalline protein. J Biol Chem 241 1763-1768. 

On the other hand, as biological molecules become larger their tendency to be associated with water molecules, metal ions, and other materials increases. Crystalline proteins, for example, routinely contain 27-65 % of the solvent used for their crystallisation 183). Such associated materials may be difficult to locate by crystallography and it may become a question of terminology whether such molecules should be regarded as inclusion complexes, non-specific aggregates, or merely contaminated biomolecules. 

Teeter, M. M. Order and disorder in water structure of crystalline proteins. Developments in Biological Standardization, Vol. 74, p. 63-72. Acting Editors Joan C. May - F. Brown. S. Karger AG, CH-4009 Basel (Switzerland), 1992... 

These organelles occur in the endosperm of cereal grains and their structures are tissue specific. They are about 2-5 im in diameter and often contain globoid and occasionally crystalloid inclusions. Prolamin accumulates in small or large spherical bodies. Crystalline protein bodies are the sites of accumulation of nonprolamin storage proteins. 

Microbodies (97-101) are spherical organelles (0.1-2.0 pm in diameter) bounded by a single membrane. They possess a granular interior and sometimes crystalline protein body. A specialized type of microbody is the glyoxysome (0.5-1.5 pm) containing enzymes ofthe glyoxy-late cycle. Glyoxysomes are found in the endosperm or cotyledons of oily or fatty seeds. 

It is suggested that crystalline proteins are explosive, as evidenced by the easily induced shattering of the microciystals currently available [1], Except, possibly, where mercuric nitrate is involved, the editor suspects this of being implosive collapse of a metastable ordering of molecules. 

Finally, we note that all transfers to alcohol-water mixtures or additions of alcohol to crystal mother liquor involve changes in the proton activity of the solution. Care must be taken to ensure that the pH does not change too much, or the crystal may be disrupted. Worse still, the enzymatic activity may be abolished. Control of proton activity in mixed solvents is discussed in Section III,D. If dielectric effects are controlled and pH is properly adjusted, the microenvironment of a crystalline protein will correspond closely to that of aqueous solution at room temperature. Such correspondence is essential for temporal resolution of individual steps in a catalytic reaction. 

There are three methods of collecting high-resolution X-ray diffraction data diffractometry, photographically, and by electronic area detector. Each method has advantages and disadvantages for a particular crystalline protein, but for very accurate data acquisition beyond 2 A... 

Measurements of x ) as a function of temperature should also establish whether or not static disorder dominates the apparent dynamics in a crystalline protein. If the lattice disorder term is the major con-... 

Figure 13.12 shows images of purified a-crystalline protein molecules sprayed on mica in water solution and then dehydrated. The proteins have very low stiffness. Mica is a suitable substrate as its cleavage planes are atomically... 

Fig. 13.12. Eye a-crystalline proteins deposited on a freshly cleaved sheet of mica (a) AFM (b) UFM 875 nm x 875 nm. The proteins are less stiff than mica. On mica surface proteins have a globular shape with 50 nm diameter on average and height a few nanometres (Dinelli etal. 2000b).

Last, but by no means least, reference should be made to the use of proteins in nano-fabrication [492]. One approach is illustrated by the fabrication of a 1-nm-thick metal film with 15-nm-diameters holes, periodically arranged on a triangular protein lattice [493]. Advantage was taken of the 10-nm-thick, uniformly porous surface (or S) layer of the crystalline protein obtained from the thermophilic bacterium Sulfolobus acidocaldarius. The protein was adsorbed from a dilute solution onto a molecularly smooth carbon-film surface, metal coated by evaporation, and ion milled to give spatial ordering of holes with the same nanometer periodicity as the protein lattice [493]. 

Figure 1. Solubility behavior of a pure crystalline protein...

But where there is an equilibrium among two or more conformations of the enzyme in solution, crystallization may select out only one of the conformations. a-Chymotrypsin has a substantial fraction of an inactive conformation present under the conditions of crystallization, but only the active form of the enzyme crystallizes. An allosteric effector molecule that changes the conformation of the protein in solution may have no effect on the crystalline protein, as, for example, with phosphorylase b.5A The enzyme is frozen in one conformation, with the crystal lattice forces preventing any conformational change. On the other hand, the addition of an effector to phosphorylase a causes the crystals first to crack and then to anneal, giving crystals of the enzyme in a second conformation. 

To some individuals, especially those who recall their experiences in organic chemistry laboratory, the ultimate step in purification of a molecule is crystallization. The desire to obtain crystalline protein has long been strong and many proteins have been crystallized. However, there is a common misconception that the ability to form crystals of a protein ensures that the protein is homogeneous. For many reasons (entrapment of contaminants within crystals, aggregation of protein molecules, etc.), the ability to crystallize a protein should not be used as a criterion of purity. The interest in pro-... 

PERUTZ. MAX F. (1914-2002). An Austrian molecular biologist and recipient of the Nobel prize for chemistry in 1962 along with John C. Kendrew, His work was concerned with crystalline protein structure, particularly the molecular structure of hemoglobin and myoglobin. His education was in England and Austria. 

The enzyme urease was not discovered until 1926 (by Sumner). It was the first enzyme to be isolated as a crystalline protein. Sumner s accomplishment confirmed the then growing belief that enzymes, the... 

Protein purification has a >200-year history the first attempts at isolating substances from plants having similar properties to egg albumen, or egg white, were reported in 1789 by Fourcroy. Many proteins from plants were purified in the nineteenth century, though most would not be considered pure by modern standards. A century later, ovalbumin was the first crystalline protein obtained (by Hofmeister in 1889). The year 1989 may not go down in history as a milestone in protein chemistry, but since then there has been a resurgence of interest in proteins after more than a decade of gene excitement. 

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