Peptides terms Links

UCHs are cysteine proteases in that the critical residue in the catalytic site is a cysteine. In addition, histidine and aspartate residues are critical for catalytic activity. All UCHs contain these residues even if they do not share a high degree of homology elsewhere in the sequence. For example, the Aplysia UCH (Ap-uch) critical for the induction oflong-term facilitation has only 39% homology to its human counterpart UCH-Lf. Ap-uch and UCH-Ll both contain the catalytic cysteine, histidine, and aspartate residues at similar positions in the molecule. UCHs cleave small peptide chains linked to the C-terminus of ubiquitin. UBPs can cleave the isopeptide bond between ubiquitins in a polyubiquitin chain and the isopeptide bond between the ubiquitin and the substrate. 

Resistin (FIZZ3), a member of a family of cysteine-rich secreted proteins termed FIZZ or RELM. Resistin is known as adipocyte-specific secretory factor. It is produced in adipose tissue. The name was coined because resistin was reported in 2001 to antagonize insulin action in cells both in vivo and in vitro, and circulating levels were increased in obese and diabetic mice. Human resistin circulates in blood as a dimer consisting of two linear 92-peptide chains linked by a disulfide bridge at Cys. Actions of resistin in humans are not well established [C. M. Stephan et al.. Nature 2001, 409, 307 U. Smith, Obes. Res. 2002, 10, 61 B. Aruna et al.. Biochemistry 2003, 42, 10554 U. Meier, A. M. Gressner, Clin. Chem. 2004, 50,1511]. 

Superose gel material of Pharmacia Biotech is a highly epichloro-hydrine cross-linked agarose matrix that has a pH range of 3-12 (short term 1-14). Hydrophilic interactions may be noticeable for lipids, peptides, and small aromatic compounds, but such interactions might even improve resolution. Superose medium is available in two different porosities Superose 6 HR 10/ 30 (bead size 13 2 /um maximum pressure 1.5 MPa) and Superose 12 HR 10/30 (bead size 10 2 /um maximum pressure 3.0 MPa). 

Peptide is the name assigned to short polymers of amino acids. Peptides are classified by the number of amino acid units in the chain. Each unit is called an amino acid residue, the word residue denoting what is left after the release of HgO when an amino acid forms a peptide link upon joining the peptide chain. Dipeptides have two amino acid residues, tripeptides have three, tetrapeptides four, and so on. After about 12 residues, this terminology becomes cumbersome, so peptide chains of more than 12 and less than about 20 amino acid residues are usually referred to as oligopeptides, and, when the chain exceeds several dozen amino acids in length, the term polypeptide is used. The distinctions in this terminology are not precise. 

Proteins are large biomolecules made up of a-amino acid residues linked together by amide, or peptide, bonds. Chains with fewer than 50 amino acids are often called peptides, while the term protein is reserved for larger chains. Twenty amino acids are commonly found in proteins all are a-amino acids, and all except glycine have stereochemistry similar to that of l sugars. In neutral solution, amino acids exist as dipolar zwitterions. 

In terms of their molecular structures, the nucleotide and protein realms are usually considered to be rather independent of each other. However, these two families of molecules are covalently linked in the translational aminoacyl- RNAs and ribonucleoproteins as well as in the nucleoproteins involved in cellular and viral replication. In these hybrid biomolecules, a (deoxy)ribose phosphate moiety serves as the structural connection between the nucleoside and peptide moieties. 

In peptide chemistry, the term "pseudopeptide" is commonly used to denote a peptide in which some or all of the amino acids are linked together by bonds other than the conventional peptide Linkage (13). Such pseudopeptides have found applications as specific structural... 

In today s discussion of the origin of life, the RNA World (Chapter 6) is seen as much more important, and is much better publicized, than the protein world . However, nucleic acids and proteins are of equal importance for the vital metabolic functions in today s life forms. Peptides and proteins are constructed from the same building blocks (monomers), the aminocarboxylic acids (generally known simply as amino acids). The way in which the monomers are linked, the peptide bond, is the same in peptides and proteins. While peptides consist of only a few amino acids (or to be more exact, amino acid residues), proteins can contain many hundreds. The term protein (after the Greek proteuein, to be the first) was coined by Berzelius in 1838. 

The G-protein that has been termed Gp, and that is linked to phospholipase C activation, may in fact be Gaj 2 or Gc. 3. Ga is designated as the G-protein responsible for activation of phospholipase A2, which results in arachidonic acid release. Some experimental evidence indicates that, at least in HL-60 cells, different agonists can preferentially activate different phospholipases, and some of these are responsible for the activation of secretion. In neutrophils, the two pertussis-toxin-sensitive Ga-proteins (Gaj-2 and G j 3) have been identified by peptide mapping of proteolytic digests of the proteins, by peptide sequencing and by immunoblotting. Complementary-DNA clones for the mRNA of these two molecules have also been isolated from an HL-60 cDNA library. Gai-2 is five to ten times more abundant than Gai.3, the former component comprising 3% of the total plasma membrane proteins. It is possible that these two different Ga-subunits are coupled to different phospholipases (e.g. phospholipases C and D). Pertussis toxin inhibits the secretion of O2 after stimulation of neutrophils by fMet-Leu-Phe, but pertussis-toxin-insensitive G-proteins are also present in neutrophils. These may be members of the Gq family and may be involved in the activation of phospholipase Cp (see 6.3.1). 

A peptide is any compound produced by amide formation between a carboxyl group of one amino acid and an amino group of another. The amide bonds in peptides are called peptide bonds. The word peptide is usually applied to compounds whose amide bonds (sometimes called eupeptide bonds) are formed between C-1 of one amino acid and N-2 of another, but it includes compounds with residues linked by other amide bonds (sometimes called isopeptide bonds). Peptides with fewer than about 10-20 residues may also be called oligopeptides those with more residues are called polypeptides. Polypeptides of specific sequence of more than about 50 residues are usually known as proteins, but authors differ greatly on where they start to apply this term. 

In spite of the aforementioned points of resemblance between the antigenic structures of Mb and lysozyme, the antigenic sites of these two proteins are radically different In structural terms (4). The five antigenic sites of Mb are each made up of residues tTTat are directly linked to one another by peptide bonds (U. 

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