Proteins varied sequence

Consensus sequence. In nucleic acids, the average sequence that signals a certain type of action by a specific protein. The sequences actually observed usually vary around this average. 

Sequence repeats in proteins vary greatly. Some are very short and others are extremely long. The repeats can be exact or approximate, they can contain residues that are absolutely conserved in some positions but not in others, and they can be extremely imprecise in other than a conserved general character. Some repeats are fixed in length and others are not. Some are primarily functional and, in an apparent contradiction in terms, can also vary in length. Some repeats occur many times... 

Phylogenetic trees based on either rRNA [2,50] or r-protein [ 170] sequence data support a monophyletic origin for the archaea. However, the evolutionary distance of the three domains relative to each other varies when different macromolecules are used[170,171]. 

Each protein consists of a polypeptide chain that is made up of residues or amino acids linked together by peptide bonds. The polypeptide chain backbone, a portion of which is shown in Fig. 2, is composed of repeating units that are identical, except for the chain termini. Proteins vary widely in size, from 50 to 500 or so residues, corresponding to 1000 to 10,000 or so atoms. Approximately half of the atoms are hydrogens, which are not seen except in very high resolution X-ray and in neutron crystal structures thus, most of the descriptions of proteins focus on the positions of the heavy atoms, C, N, O, and S. What distinguishes different proteins, other than the number of amino acids, is the sequence of amino acids in the polypeptide chain. There are 20... 

Although the a-helical core is common to all IF proteins, the N- and C-terminal domains of different types of IF proteins vary greatly In molecular weight and sequence. Partly because of this lack of sequence conservation, scientists initially speculated that the N- and C-terminal domains do not have roles in IF assembly. The results of several subsequent experiments, however, proved this hypothesis to be partly incorrect. For instance, if the N-terminal domain of an IF... 

Deoxyribonucleic Acid (DNA). The structure of DNA is well known. Its function is to transmit genetic information. The characteristics of all cells are determined by their proteins, particularly the enzymes. The characteristics of a protein are in turn determined by its unique sequence of amino acid residues. DNA contains the master plan for protein formation in its base sequence. The particular sequence of the bases adenine (A), thymine (T), guanine (G), and cytosine (C) thus represent a code. Since all proteins consist of 20 different L-amino acids, the genetic code then directs the varying sequences specific for a given protein. 

Comparison of the compressibilities of polymorphs and of the crystal structures of separate amino acids might be relevant to understand why fragments of proteins built of amino acids in varied sequences compress variously [88, 192, 193]. 

In this chapter, we refer to polypeptides and proteins, and we now give a brief resume of some of the terminology needed. A polypeptide in Nature is formed by the condensation, in varying sequences, of the 20 naturally occurring a-amino acids. Structure 28.1 gives the general formula of an amino ... 

In every living cell, proteins are assembled on ribosomes by the co-polymerization of about 20 kinds of amino acids, all with the same L-optical configuration (see Fig. 5.7). The molecular weight of proteins varies from about 6000 to well over a million, but all have the common structure shown in Fig. 4.2, where R represents the familiar side-chains, such as methyl (for alanine) and j -hydroxy-benzyl (for tyrosine). The Atlas of Protein Sequence and Structure (National Biomedical Research Foundation, Georgetown University, Washington, D.C.), published at intervals, contains the amino acid sequences of many hundreds of proteins (for other lists, see Section 17.4). 

Boundless Potential of Biosynthesis to Produce Proteins of Varied Sequence... 

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