Signal sequences interactions

Odorants are thought to bind to integral membrane receptors on the cilia of the olfactory sensory neurons. The receptors are thought to he specific different olfactory neuron types recognize different odorants that share certain characteristics (Buck, 1993). The odorant receptors transduce signals via interactions with G-proteins (so-called because guanosine trisphosphate is involved in their activation). These G-protein-coupled exhibit seven hydrophobic domains (Fig. 5.6). Variation in the amino acid sequence of the transmembrane domain may account for specificity and selectivity of odor reception. 

Signal sequences and translocation. In 1971, Blobel and Sabatini postulated that for some proteins an N-terminal segment of newly synthesized polypeptide chains contains a signal sequence or leader peptide of 15-30 amino acids which carries information concerning the location of the mature protein in the cell.23 280 The rather nonpolar signal sequences of proteins destined for secretion from cells would interact... 

Ear less is known about the process of flavivirus assembly. Electron microscopy has shown that immature virions can be found in the lumen of the endoplasmic reticulum (Murphy, 1980). The nucleocapsid core is not assembled free in the cytoplasm rather, its assembly appears to take place on the cytoplasmic face of membranes with which prM and E proteins are associated (Khromykh et al., 2001). The carboxy-terminal signal sequence of the precursor to the capsid protein is thought to anchor that protein to the membrane (Amberg et al., 1994). This should allow interactions to occur between the capsid protein and the envelope proteins, which are also anchored to the membrane but reside in the lumen of the endoplasmic reticulum or vesicles. The capsid protein also contains a conserved stretch of hydrophobic residues located roughly in the middle of the protein that has been suggested to serve as an additional or alternative membrane anchor (Markoff et al., 1997). 

A Model for the Initial Interactions of Signal Sequences with the... 

It has been suggested that the hydrophobic region may be involved in specific interactions, for example, with SRP (Emr et al., 1980 Silhavy et al., 1983). Clearly the mutations described above, as well as substitutions of j8-hydroxyleucine for leucine, could disrupt such interactions and cause an export defect. However, the wide variation of signal sequences, and their interchangeability, argue against its specific recognition on the basis of sequence. 

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