Terminator sequences

FIGURE 28 10 During transcription a molecule of mRNA is assembled from a DNA template Transcription begins at a promoter sequence and proceeds in the 5 3 direction of the mRNA until a termination sequence of the DNA is reached Only a region of about 10 base pairs is unwound at any time... 

The group of peptides known as tachykinins include substance P, substance K or neurokinin A, and neuromedin K, ie, neurokinin B, as well as a number of nonmammalian peptides. All members of this family contain the conserved carboxy-terrninal sequence Phe-X-Gly-Leu-Met-NH2, where X is an aromatic, ie, Phe or Tyr, or branched aliphatic, eg, Val or lie, amino acid. In general, this C-terminal sequence is cmcial for tachykinin activity (33) in fact, both the methionineamide and the C-terminal amide are cmcial for activity. The nature of the X residue in this sequence determines pharmacological identity (34,35) thus the substance P group contains an aromatic residue in this position, while the substance K group contains an aliphatic residue (33). 

Sequences have been determined for plasminogen and bovine Factor XII, and they are not homologous with the other serine proteases. The amino-terminal sequence of Factor XII is homologous, however, with the active site of several naturally occurring protease inhibitors (11). 

In some cases, whole parts of the protein are missing from the experimentally determined structure. At times, these omissions reflect flexible parts of the molecule that do not have a well-defined structure (such as loops). At other times, they reflect parts of the molecule (e.g., terminal sequences) that were intentionally removed to facilitate the crystallization process. In both cases, structural models may be used to fill in the gaps. 

FIGURE 9.19 Proteins containing the C-terminal sequence CAAX can undergo prenylation reactions that place thioether-linked farnesyl or geranylgeranyl groups at the cysteine side chain. Prenylation is accompanied by removal of the AAX peptide and methylation of the carboxyl group of the cysteine residue, which has become the C-terminal residue. 

Edman degradation (Section 26.6) A method for N-terminal sequencing of peptide chains by treatment with Af-phenylisothiocyanate. 

The neuropeptides are peptides acting as neurotransmitters. Some form families such as the tachykinin family with substance P, neurokinin A and neurokinin B, which consist of 11 or 12 amino acids and possess the common carboxy-terminal sequence Phe-X-Gly-Leu-Met-CONH2. Substance P is a transmitter of primary afferent nociceptive neurones. The opioid peptide family is characterized by the C-terminal sequence Tyr-Gly-Gly-Phe-X. Its numerous members are transmitters in many brain neurones. Neuropeptide Y (NPY), with 36 amino acids, is a transmitter (with noradrenaline and ATP) of postganglionic sympathetic neurones. 

As discussed above, for all smooth muscle cells, the terminal sequence of the signal transduction pathways which regulates contraction seems to be the same. As... 

A protein, designated cyctochrome c", isolated from the methylotrophic bacterium Methylophilus methylotrophus, has been studied extensively because of its unusual properties and was found to have an average molecular mass of 14293.0 Da and to contain 124 amino acid residues. The A-terminal sequence to residue 62 had been determined and the heme binding site had been located at Cys-49 and Cys-52 [12]. Further studies were concerned with determining the remainder of the sequence. 

Amino terminal sequence (20-80 residues) Mitochondrial matrix... 

Recently, a gene coding for a novel pectin methylesterase, has been cloned (19). This gene, pemB, codes for a 433 amino add protein induding a N-terminal sequence of 21 amino adds which presents the characteristics of lipoprotein... 

Up to now, the pectinolytic enzymes of E. chrysanthemi that have been detected were extracellular secreted enzymes (PelA, B, C, D, E, L, exo-Peh and PemA), periplasmic (exo-Pel), or cytoplasmic (OGL) proteins (1, 5). In contrast, PemB is an outer membrane pectinolytic enzyme. To our knowledge it is the first pectinase characterised as a membrane protein. We presented several lines of evidence showing that PemB is a lipoprotein (i) Its N-terminal sequence has the characteristics of lipoprotein signal sequences, (ii) PemB is synthesised as a high molecular weight precursor processed into a lower molecular weight mature form, (iii) Palmitate, the most prevalent fatty acid in bacterial lipoproteins (12), is incorporated into PemB. 

Hall et al. [62] identified in a separate study the same glycoprotein in H,K-ATPase vesicles isolated from porcine gastric mucosa. A stoichiometric ratio of 1.2 1.0 was found for the deglycosylated protein (35 kDa)/catalytic 94-kDa protein. Furthermore, compelling evidence that this glycoprotein is the H,K-ATPase p subunit was provided by N-terminal sequence analysis of three protease V8-obtained peptides of the 35-kDa core protein. These peptides showed 30% and 45% homology with the Na,K-ATPase pi and pi subunit, respectively. 

SERCA-type -ATPases from non-mammalian cells (SERCAMED) Sequences of SERCA-type Ca -ATPases were also obtained from Plasmodium yoelii [68], Anemia [69] and Drosophila [70], These enzymes are similar in size to the SERCAl- and SERCA2a-type Ca -ATPases from mammalian muscles, but based on their N- and C-terminal sequences they represent a distinct group. In spite of the wide philogenetic variations between them they all share a common N-term-inal sequence (MED) that differs from mammalian enzymes. None of the corresponding proteins were isolated and characterized. 

The molecular weights of all SERCA-type Ca " transport ATPases are in the range of 100-110 kDa. Their N-terminal sequences are similar Met-Glu-X(Ala, Asn, Glu, Asp)-X (Ala, Gly, He). The Met-Glu-X-X sequence serves as a signal for the acetylation of N-terminal methionine both in soluble and in membrane proteins [71,72]. 

There are at least five distinct isoforms of plasma membrane Ca -ATPases in mammalian tissues that differ in distribution and C-terminal sequences [34]. The molecular weight of these enzymes is in the range of 127 300-134683 (Table I) and they all contain calmodulin-binding domains [3], in contrast to the much smaller ( 110kDa) SERCA enzymes that are calmodulin independent. 

The slow and fast isoenzymes of Ca -ATPase contain 42 and 50 arginine residues, respectively. The C-terminal sequence of the neonatal fast-twitch isoenzyme is Arg-Arg-Lys. There are only four arginine residues in the putative transmembrane helices, which are probably located near the cytoplasmic or luminal surface of the membrane. The remaining arginine residues are distributed in the cytoplasmic domains. 

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