Polypeptides major effects

Proteins SP-B and SP-C are small extremely hydrophobic polypeptides consisting of 79 and 35 amino acid residues, respectively." 0 Aliphatic branched amino acids constitute 23 of the 35 residues of the C-terminal part of protein C, which is also palmitoylated on two cysteine residues. SP-B is formed from a large 381-residue precursor. The mature protein contains seven cysteines and disulfide bridges. Both proteins have major effects on the properties of the surfactant mixture. They promote rapid reorganization of lipid layers, an important consideration for the functioning of the surfactant. Infants lacking SP-B suffer severe respiratory failure with high mortality.6... 

The chief hormones of the iteurohypophysis are the polypeptides oxytocin and vasopressin. The hormone characteristic of the pars intermedia Is the melanocyte-stimulating hormone. It is usually spoken of in the plural, since in most mammals both alpha and beta forms are known. The structures of the liist two arc shown In the Table I. The most prominent effect of oxytocin is the contraction ot smooth muscle, especially of the uterus, It also has a major effect upon the muscles about ihe breast, and so stimulates the ejection of milk in I,totaling animals. It has a delinile stimulating effect upon (he muscles of Ihe ureter, urinary bladder, intestine, and gall bladder. 

The sequence of amino acids—the primary structure—helps dictate the protein s final shape. A substitution of just one amino acid in the polypeptide sequence can have major effects on the final shape of the protein. 

Synthetic drugs of comparable selectivity and affinity to the 1,4-dihydropyridines do not yet exist for the other channel types, T, N, P/Q, and R these remain characterized by complex polypeptide toxins of the aga- and conotoxin classes. Neuronal pharmacology, including that of the central nervous system (CNS), is dominated by the N, P/Q, and R channels. This underscores the normally weak effect of L-channel antagonists on CNS function. Drugs that act at the N, P, and R channels with comparable selectivity and affinity to the 1,4-dihydropyridines may be expected to offer major potential for a variety of CNS disorders, including neuronal damage and death from ischemic insults. 

These diverse effects are mediated by multiple receptors designated Y through Y 6. All receptors except Y3 have been cloned and shown to be G protein-coupled receptors linked to mobilization of Ca2+ and inhibition of adenylyl cyclase. Yj and Y2 receptors are of major importance in the cardiovascular and other peripheral effects of the peptide. Y4 receptors have a high affinity for pancreatic polypeptide and may be a receptor for the pancreatic peptide rather than for NPY. Y5 receptors are found mainly in the central nervous system and... 

Other species of amanita are among the deadliest fungi known. Polypeptide-like toxins in Amanita phalloides, or death cup, can prove fatal or at the very least can cause permanent liver and kidney damage. These mushrooms are common in the temperate climates of Europe and North America. They are responsible for the majority of what is called "slow" mushroom poisoning in the U.S. In fact, it was only a few years ago that the local newspaper reported a case of amanita poisoning within SLO county. Mushroom poisoning is known as mycetism. In addition the amanita also contain bufotenine which has CNS effects. See the ASIDE which discusses the peptide poisons. 

The biological function of peptides and proteins depends on their native conformation. The side-chain functionalities of the a-amino acids that comprise peptides and proteins have profound effects on their properties. These functionalities reside in the 20 naturally occurring a-amino acids, which have different propensities for formation of the three major secondary structural conformations. 1 In addition to these naturally occurring a-amino acids whose primary structure enables the polypeptide to fold into a predictable secondary and tertiary structure, the incorporation of unnatural amino acids has opened important areas of research. 

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