Amino sequence similarity

Amylin [106602-62-4] (75) (Fig. 4) is a 37-amino acid peptide having approximately 46% sequence similarity to CGRP (33). Amylin is present ia pancreatic P-ceUs along with insulin. It may function as a hormone ia glucoregulation and has been proposed as an etiologic factor ia certain forms of diabetes. Amylin is also present ia dorsal root ganglia (see INSULIN AND OTHER ANTIDIABETIC DRUGS). 

Proteins have unique amino acid sequences, and it is this uniqueness of sequence that ultimately gives each protein its own particular personality. Because the number of possible amino acid sequences in a protein is astronomically large, the probability that two proteins will, by chance, have similar amino acid sequences is negligible. Consequently, sequence similarities between proteins imply evolutionary relatedness. 

Amino acid sequence analysis reveals that proteins with related functions often show a high degree of sequence similarity. Such findings suggest a common ancestry for these proteins. 

In cyclic nucleotide-regulated channels, this domain serves as a high-affinity binding site for 3-5 cyclic monophosphates. The CNBD of channels has a significant sequence similarity to the CNBD of most other classes of eukaryotic cyclic nucleotide receptors and to the CNBD of the prokaryotic catabolite activator protein (CAP). The primary sequence of CNBDs consists of approximately 120 amino acid residues forming three a-helices (oA-aC) and eight (3-strands ( 31- 38). 

Consensus sequences similar to ori or ARS in structure or function have not been precisely defined in mammalian cells, though several of the proteins that participate in ori recognition and function have been identified and appear quite similar to their yeast counterparts in both amino acid sequence and function. 

Figure 3. Comparison of the amino acid sequence of RHG of A. aculeatus with polygalacturonases PGI, PGII and PGC of A. niger. The most homologous region of the proteins is shown. Numbering is from the first amino acid of the signal peptide. Identical amino acids similar amino acids. The amino acid residues in bold type are referred to in the text.

Drosophila DDC belongs to a family of pyridoxal-dependent decarboxylases that extends from prokaryotes to eukaryotic plants and animals. The members of this family show significant sequence similarity over much of their length, even though the individual proteins have quite different substrate specificities, including the amino acids tyrosine, tryptophan, phenylalanine, histidine, and glutamate, and the amino acid derivatives... 

The amino acid sequence similarities of all 36 PHA synthases were pairwise revealed, and the results of this comparison are compiled in Table 2. The data correspond well with phylogenetic tree shown in Fig. 1, and the similarities va-... 

Wells, R. G. and M. A. Hediger. Cloning of a rat kidney cDNA that stimulates dibasic and neutral amino acid transport and has sequence similarity to glucosidases. Proc. Natl. Acad. Sci. U. S. A 1992, 89, 5596-5600. 

Lever. Cloning and expression of a mammalian Na+/amino add cotransporter with sequence similarity to Na-L/glucose cotransporters./. Biol. Chem. 1993, 268, 1509-1512. 

Cloning of the rat pi opioid receptor was somewhat easier than the cloning of the <5 receptor since it was based on the knowledge of what the 3 receptor sequence was and on the assumption that 3 and pi receptors had high amino acid sequence similarity. Chen et al. [18] used probes directed against conserved regions of the 6 receptor to screen a rat brain cDNA library. cDNAs identified by this approach were cloned into expression vectors, transfected into COS cells and pi receptor expression detected with radioactive pi receptor selective ligands. 

The k receptor was cloned by a completely different approach. Yasuda et al. [9] employed probes against conserved regions of somatostatin receptors to screen a mouse brain cDNA library. Mouse k and 3 receptor cDNAs were isolated using this procedure that established that opiate and somatostatin receptors have high amino acid sequence similarity, consistent with their ability to bind some common ligands, such as Sandostatin. 

B. Henrissat, A classification of glycosyl hydrolases based on amino acid sequence similarities, Biochem. J., 280(Pt 2), (1991) 309-316. 

Within each of these adhesion molecule families, membership has been defined largely by amino-acid sequence similarity, which is reflected in common structural features. Consequently, distinct binding requirements also characterize each family. For example, cadherins interact in a Ca2+-dependent, usually homophilic manner. Binding of the members of the Ig family is Ca2+-independent and, although frequently homophilic, can be heterophilic. Integrin binding is also divalent cation-dependent (Ca2+, Mg2+) but always heterophilic. 

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