Prosthetic group globular

Myoglobin was the first protein to have its three-dimensional structure solved by X-ray crystallography. It is a globular protein made up of a single polypeptide chain of 153 amino acid residues that is folded into eight a-helices. The heme prosthetic group is located within a hydrophobic cleft of the folded polypeptide chain. 

Each monomer of COX consists of three structural domains a short N-terminal epidermal growth factor domain, a membranebinding domain, and a large, globular C-terminal catalytic domain (Fig. la) (3). The COX and POX active sites are located on opposite sides of the catalytic domain with the heme prosthetic group positioned at the base of the peroxidase... 

Haem peroxidases are globular proteins with an iron-porphyrin complex as a prosthetic group. These enzymes are widespread among prokaryotes and eukaryotes. They catalyze the oxidation of substrates by organic peroxides or hydrogen peroxide. During the past decades, considerable scientific effort has been put into elucidation ofthe mechanisms of reactions catalyzed by these enzymes. Pulse radiolysis technique has made an important contribution by providing information on the redox states of the enzymes and their interconversion, as well as on the properties ofthe free radical intermediates involved [23]. 

Globin The globular proteins that are the polypeptide components of myoglobin and hemoglobin. They contain a hydrophobic pocket that holds the heme prosthetic group. 

For a globular protein, considerably more information is needed. It is necessary to determine the way in which the helical and pleated-sheet sections fold back on each other, in addition to the positions of the side-chain atoms and any prosthetic groups. The interactions between the side chains play an important role in the folding of proteins. The folding pattern frequently brings residues that are separated in the amino acid sequence into proximity in the tertiary structure of the native protein. 

Many globular proteins contain prosthetic groups with metal ions and sensitive thiol groups which may be poisoned by slow leakage of metal ions from the welding in the joints of stainless steel equipment. To overcome this potential problem, two manufacturers have designed equipment to minimise contact with any stainless steel. 

The ribbon representation shows transmembrane a-helices traversing through the lipid bilayer membrane, containing heme b prosthetic groups, the Qo and Q sites, and the FeS center at the tip of the globular component of the RIP and associated with the Q site. 

Acyl carrier protein, ACP a small, acidic, heat-stable globular protein which is part of the fatty acid synthesizing complex in . coli and other bacteria, yeast and plants. It carries the fatty acid chain during biosynthesis of the latter. The ACP from E. coii contains 77 amino acids (M, 8,847), and the primary structure is known. Sulfiir-containing amino adds are absent, but a molecule of phosphopantetheine (which possesses -SH) is linked to the protein via a phosphate ester to the hydroxyl of serine 36. All ac l residues formed during fatty acid biosynthesis are bound as thioesters to the SH of this prosthetic group. The M, of isolated ACP lie between 8,600 (Clostridium butyrkum) and 16,000 (yeast). 

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