Signal peptide domains

Another interesting part to explore is the feature section, which displays characteristics of the protein displayed, such as signal peptides, domains, transmembrane regions, or repeated sequence segments. 

Fig. 1 Primary structure of human tropoelastin isoform 3 (EBI accession no. P15502). The highlighted regions correspond to the signal peptide and hydrophobic and hydrophilic domains. Based on [2]...

Its length can vary from 30 to more than 100 residues. It is rich in serine and threonine but deficient in acidic residues. It is not clear whether it has the three-domain structure like the signal peptide (von Heijne et al., 1989). Recently, a chloroplast-processing enzyme was identified as the general stromal processing peptidase (Richter and Lamppa, 1998). 

The inner envelope membrane proteins have a cleavable N-terminal transit peptide, as well as some hydrophobic domain (s) in their mature portion. There are two possibilities on the role of this hydrophobic domain it may work as an N-terminal signal peptide after the translocation into the stroma and the subsequent cleavage of the transit peptide. Alternatively, it may work as a stop-transfer signal. One more important question is how the distinction is made between the outer membrane proteins, the inner membrane proteins, and the thylakoid membrane proteins. It is still an enigma. 

Fig. 4. A schematic representation of alternatively spliced Fas mRNA variants and the proteins they encode in normal PBMC. The upper three variants of FasA(4, 7), FasA(3, 4), and FasA(3, 4, 6) and the lower two variants of FasA(3, 4), and FasA(4, 6) were reported by Liu et al. (L6) and Papoff et al. (PI), respectively. The solid line indicates regions lacking in Fas mRNAs. The regions that are translated or not translated into proteins are indicated by boxes and broken lines, respectively. LR leader peptide CR, cysteine-rich subdomain TM, transmembrane domain ST, signal-transducing domain NR, negative regulation domain AL, altered amino acid region.

---