C-terminal sequences

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). 

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. 

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. 

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. 

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. 

The authors expressed PKA consisting of 353 amino acids, of which eight are prolines. Resonances of 274 backbone amide peaks were visible in the spectrum, of which 191 were assigned. It was possible to assign resonances for the N- and C-terminal sequences, the majority of the N-lobe, including the glycine-rich loop, and most of the solvent-exposed residues of the C-lobe. This enabled a determination of the structure for the more flexible parts of the structure. However, many correlations were missing for the... 

HSAB and sulfo-HSAB have been used to investigate serum amyloid A (Cai et al., 2007), the functional role of C-terminal sequence elements in the transporter associated with antigen processing (Ehses et al., 2005), and the kinetics of intermolecular interactions during cytochrome C protein folding (Nishida et al., 2004). 

As well as fluorescence-based assays, artificial membranes on the surface of biosensors offered new tools for the study of lipopeptides. In a commercial BIA-core system [231] a hydrophobic SPR sensor with an alkane thiol surface was incubated with vesicles of defined size distribution generating a hybrid membrane by fusion of the lipid vesicles with the alkane thiol layer [232]. If the vesicles contain biotinylated lipopeptides their membrane anchoring can be analyzed by incubation with streptavidine. Accordingly, experiments with lipopeptides representing the C-terminal sequence of N-Ras show clear differences between single and double hydrophobic modified peptides in their ability to persist in the lipid layer [233]. 

The insertion stability of several lipopeptides of the C-terminal sequence of N-Ras in such an artificial membrane is shown in Scheme 14. Here strepta-vidine is applied to indicate biotinylated lipopetides on the membrane surface. 

Hardeman K., Samyn B., Van der Eycken J., and Van Beeumen J. (1998), An improved chemical approach toward the C-terminal sequence analysis of proteins containing all natural amino acids, Protein Sci. 7, 1593-1602. 

Li J. and Liang S. (2002), C-terminal sequence analysis of peptides using triphe-nylgermanyl isothiocyanate, Anal. Biochem. 302, 108-113. 

C-terminal sequences of Ni-binding subunits in NiFe(Se) hydrogenases and C-terminal processing... 

Partial digestion of human haemoglobin by carbox rpeptidases A and B has shown that chemical modifications to the -chains are more effective in destroying haem-haem interaction than those to the a-chains while modifications to either chain decrease the magnitude of the Bohr effect. The C-terminal sequences of the two types of chain of human haemoglobin are as follows ... 

The distinguishing feature of CS H2A is a nine amino acid extension on its C-terminus. The possibility that CS H2A is the sea urchin H2A.X has been raised on the basis of its structure and its similarity to a large H2A stored in Xenopus eggs that was identified as H2A.X [127] this Xenopus protein has been identified as H2.X on the basis of its position in two dimensional gels and its peptide map [129], but its sequence has not been determined. The C-terminal sequence of CS H2A (SMEY) resembles the SQ(ED)(ILFY) consensus of H2AX. The Xenopus and sea urchin proteins also show similar phosphorylation patterns during chromatin assembly [128,129]. Additional studies will be required to determine the relationship, if any, between CS H2A and H2A.X. 

Mannironi, C., Bonner, W.M., and Hatch, C.L. (1989) H2A.X a histone isoprotein with a conserved C-terminal sequence, is encoded by a novel mRNA with both DNA replication type and poly A 3 processing signals. Nucleic Acids Res. 17, 9113-9125. 

H2A.1, H2A.2, and H2A.X are phosphorylated at serine residue 1 [8,9]. H2A.Z is not phosphorylated. In vitro protein kinase C phosphorylates H2A at serine residue 1 [10]. Telrahymena H2A is phosphorylated in the C-terminal sequence [11]. Tetrahymena H2A.1 is phosphorylated at serine residues 122, 124, and 129, while H2A.2 is modified at serine residues 122 and 128 (Fig. 3). Phosphorylation of H2A occurs in the transcriptionally active macronucleus of Tetrahymena thermophila, but not in the transcriptionally inert micronucleus [12]. Tetrahymena H2A variant hvl is phosphorylated [13]. H4, like H2A, is phosphorylated at N-terminal serine... 

Wellmann F, Matern U, Lukacin R (2004) Significance of C-terminal sequence elements for petunia flavanone 3 )-hydroxylase activity. FEBS Lett 561(1-3) 149-154... 

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