Protein internal structure

Some specialized eukaryotic cells have cilia that show a whiplike motion. Sperm cells move with one flagella, which is much longer than a cilium but has a nearly identical internal structure called axoneme. It is composed of nine doublet MTs that form a ring around a pair of single MTs. Numerous proteins bind to the MTs. Ciliary dynein motors generate the force by which MTs slide along each other to cause the bending of the axoneme necessary for motion. 

Inoue et al. (2003) found that silk proteins will form rodlike structures and that those structure will assemble into comblike or fabric-like superstructure. The scale differences between the rods (nanometers) and the superstructure (micrometers) would suggest that the rod formation is governed by amyloid fibril formation and that the supramolecular arrangement is governed by the properties of the rod (Oroudjev et al., 2002 Putthanarat et al., 2000), namely surface interaction and hydration. Three levels of association could be considered (i) within the proteins internal /1-strands will organize to form intra /1-sheet structures, (ii) /1-sheets from neighboring molecules will associate to form fibril subunits, and (iii) the fibril subunits will further associate to form larger fibrils or rods. 

As would be expected of active protein secreting cells, glandular epithelial tissue, the cytokine secreting cells of the immune system and the blood vessel endothelium, have an extensive internal structure consisting of rough endoplasmic reticulum and numerous mitochondria. Peptide hormones, growth factors and cytokines like all proteins are synthesized by DNA transcription and mRNA translation. The primary transcript of the mRNA may code for an inactive prohormone which requires careful proteolysis to produce the active hormone, as for example in the case of insulin. Adrenocorticotropic hormone (ACTH) is particularly interesting in this respect because... 

Small molecules that act as collisional quenchers may penetrate into the internal structure of proteins, diffuse, and cause quenching upon collision with the aromatic groups. Lakowicz and Weber(53) have shown that the interaction of oxygen molecules with buried tryptophan residues in proteins leads to quenching with unexpectedly high rate constants—from 2 x 109 to 7 x 109 M l s 1. Acrylamide is also capable of quenching the fluorescence of buried tryptophan residues, as was shown for aldolase and ribonuclease 7V(54) A more hydrophobic quencher, trichloroethanol, is a considerably more efficient quencher of internal chromophore groups in proteins.(55)... 

What type of hydrogen bonds are present in the internal structure of a globular protein ... 

Crystalhzation is another typical example of self-organization. The form of the crystal lattice, say of crystallizing NaCl, is not imposed by external forces, but is the result of the internal structural parameters of the NaCl system under the given conditions (temperature, etc.). Protein folding is also a self-organization process, determined by the internal rules of the system (primarily the primary structure). As is well known, Chris Anhnsen and coworkers demonstrated in the 1970s that... 

Receptor clustering also accounts for receptor internalization. The basis of this phenomenon is endocytosis via coated pits. These pits are apparent in electron micrographs as membrane invaginations coated on the inner (cytoplasmic) side with a web of the protein clathrine. It has been suggested that certain receptor proteins have structural domains that allow them to react with coated pits. Receptor clusters in coated pits are rapidly endocytosed, resulting in the formation of vesicles (endosomes) that are then... 

Many enzymes exist within a cell as two or more isoenzymes, enzymes that catalyze the same chemical reaction and have similar substrate specificities. They are not isomers but are distinctly different proteins which are usually encoded by different genes.22 23 An example is provided by aspartate aminotransferase (Fig. 2-6) which occurs in eukaryotes as a pair of cytosolic and mitochondrial isoenzymes with different amino acid sequences and different isoelectric points. Although these isoenzymes share less than 50% sequence identity, their internal structures are nearly identical.24-27 The two isoenzymes, which also share structural homology with that of E. coli,28 may have evolved separately in the cytosol and mitochondria, respectively, from an ancient common precursor. Tire differences between them are concentrated on the external surface and may be important to as yet unknown interactions with other protein molecules. 

The polyanion-polycation complex (symplex) formation process is a phenomenon that had long been known on an empirical base from the mutual precipitation of proteins [150]. The internal structure and the properties of the resulting complexes are strongly influenced by the nature of the polymeric components and the system conditions. The polymer parameters include the molar mass, the... 

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