Characterization of the C-Terminal Propeptide Involved in Bacterial Wall Spanning of Alpha-Amylase from the Psychrophile Alteromonas Haloplanctis

• Published in: Journal of Biological Chemistry
• Main Authors: Feller, Georges, D'Amico, Salvino, Benotmane, A. M., Joly, Fabian, Van Beeumen, J., Gerday, Charles
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 1998
• Subjects: Life sciences; Biochemistry; biophysics & molecular biology; Sciences du vivant; Biochimie; biophysique & biologie moléculaire; Antarc*; Antarctic
• Online Access: https://orbi.uliege.be/handle/2268/16076; https://orbi.uliege.be/bitstream/2268/16076/1/JBC_1998_Ct.pdf; https://doi.org/10.1074/jbc.273.20.12109

peer reviewed The antarctic psychrophile Alteromonas haloplanctis secretes a Ca2+- and Cl--dependent alpha-amylase. The nucleotide sequence of the amy gene and the amino acid sequences of the gene products indicate that the alpha-amylase precursor is a preproenzyme composed by the signal peptide (24 residues), the mature alpha-amylase (453 residues, 49 kDa), and a long C-terminal propeptide or secretion helper (192 residues, 21 kDa). In cultures of the wild-type strain, the 70-kDa precursor is secreted at the mid-exponential phase and is cleaved by a nonspecific protease into the mature enzyme and the propeptide. The purified C-terminal propeptide displays several features common to beta-pleated transmembrane proteins. It has no intramolecular chaperone function because active alpha-amylase is expressed by Escherichia coli in the absence of the propeptide coding region. In E. coli, the 70-kDa precursor is directed toward the supernatant. When the alpha-amylase coding region is excised from the gene, the secretion helper can still promote its own membrane spanning. It can also accept a foreign passenger, as shown by the extracellular routing of a beta-lactamase-propeptide fusion protein.