Biomaterial Database

The conformational protential of porcine proinsulin C-peptide. 1976

H P Vogt, and A Wollmer, and V K Naithani, and H Zahn

Statistical analysis of protein sequences lends itself to the identification of regions with a definite inclination to adopt specific main-chain conformations. Application of the model of Chou and Fasman[1,2] to porcine proinsulin C-peptide localizes the tendency to form a helix in the segments (38 to 44) and (51 to 58). A tendency to beta turn formation is predicted for the segment (45 to 50). The realization of this conformational potential under native and various other conditions was examined by CD spectroscopy. Synthetic C-peptide as well as the synthetic fragments (33 - 40), (41 - 52), (41 - 61), (46 - 52), (46 - 61), and (53 - 61) were included in the study. These fragments provide breaks in the amino acid sequence in each of the potentially ordered regions. The strong helical tendency in the (51 - 58) segment can be activated in the fragments (41 - 61) and (46 - 61) by 1 per cent sodium dodecylsulfate, although the spectrum is not indicative of a classical alpha-helix. However, the conformation in the (51 to 58) segment should also be non-random in native C-peptide, since cleavage of the (46 - 61) fragment into the subfragments (46 - 52) and (53 - 61) causes considerable spectral effects. Cleavage of the other potentially helical region (38 to 44) between residues 40 and 41, on the other hand, is without spectral consequences. Therefore, this segment is unlikely to be helical in native C-peptide. In the coherent C-peptide, the helix formation which can be induced by sodium dodecylsulfate in the C-terminal part is apparently inhibited by interaction with the N-terminal half of the molecule. This interaction implies that the chain is folded back on itself, which is consistent with a high probability of bets turn formation in the segment (45 to 50). The CD spectra of the fragments (41 - 52) and (46 - 52), in which the beta turn could occur, are characterized by positive ellipticity about 213 nm. The correlation of the beta turn with this type of spectrum as well as its definite location are discussed, but cannot be proved solely on CD spectroscopic grounds.

UI	MeSH Term	Description	Entries
D010446	Peptide Fragments	Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.	Peptide Fragment,Fragment, Peptide,Fragments, Peptide
D011384	Proinsulin	A pancreatic polypeptide of about 110 amino acids, depending on the species, that is the precursor of insulin. Proinsulin, produced by the PANCREATIC BETA CELLS, is comprised sequentially of the N-terminal B-chain, the proteolytically removable connecting C-peptide, and the C-terminal A-chain. It also contains three disulfide bonds, two between A-chain and B-chain. After cleavage at two locations, insulin and C-peptide are the secreted products. Intact proinsulin with low bioactivity also is secreted in small amounts.
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D002942	Circular Dichroism	A change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Circular Dichroism, Vibrational,Dichroism, Circular,Vibrational Circular Dichroism
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000596	Amino Acids	Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.	Amino Acid,Acid, Amino,Acids, Amino
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013056	Spectrophotometry, Ultraviolet	Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Ultraviolet Spectrophotometry
D013552	Swine	Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).	Phacochoerus,Pigs,Suidae,Warthogs,Wart Hogs,Hog, Wart,Hogs, Wart,Wart Hog