title: Opportunistic proteolytic processing of carbonic anhydrase 1 from Chlamydomonas in Arabidopsis reveals a novel route for protein maturation.
abstract: Proteolytic processing of secretory proteins to yield an active form generally involves specific proteolytic cleavage of a pre-protein. Multiple specific proteases have been identified that target specific pre-protein processing sites in animals. However, characterization of site-specific proteolysis of plant pre-proteins is still evolving. In this study, we characterized proteolytic processing of Chlamydomonas periplasmic carbonic anhydrase 1 (CAH1) in Arabidopsis. CAH1 pre-protein undergoes extensive post-translational modification in the endomembrane system, including glycosylation, disulfide bond formation and proteolytic removal of a peptide 'spacer' region, resulting in a mature, heterotetrameric enzyme with two large and two small subunits. We generated a series of small-scale and large-scale modifications to the spacer and flanking regions to identify potential protease target motifs. Surprisingly, we found that the endoproteolytic removal of the spacer from the CAH1 pre-protein proceeded via an opportunistic process apparently followed by further maturation via amino and carboxy peptidases. We also discovered that the spacer itself is not required for processing, which appears to be dependent only on the number of amino acids separating two key disulfide-bond-forming cysteines. Our data suggest a novel, opportunistic route for pre-protein processing of CAH1.
authors.affiliation: Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA 50011, USA.
authors.forename: Parijat S
authors.initials: PS
authors.lastname: Juvale
authors.affiliation: Department of Biology, Millersville University, Millersville, PA 17551, USA.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Wagner
authors.affiliation: Department of Genetics, Development and Cell Biology, Iowa State University, 202 Catt Hall, Ames, IA 50011-1301, USA mspalding@iastate.edu.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Spalding
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000737:chemistry / Q000378:metabolism*; D002696:Chlamydomonas / Q000201:enzymology*; D004220:Disulfides / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion
chemical_list: D000596:Amino Acids; D004220:Disulfides; D010455:Peptides; D010940:Plant Proteins; D021122:Protein Subunits; D002256:Carbonic Anhydrases
keywords: Carbonic anhydrase; Chlamydomonas; endomembrane system; post-translational modifications; pre-protein processing; proteases.; reinhardtii