Native and Foreign Proteins Secreted by the Cupriavidus metallidurans Type II System and an Alternative Mechanism

Journal of Microbiology and Biotechnology
Houjuan Xu, Timothy P Denny


The type II secretion system (T2SS), which transports selected periplasmic proteins across the outer membrane, has rarely been studied in nonpathogens or in organisms classified as Betaproteobacteria. Therefore, we studied Cupriavidus metallidurans (Cme), a facultative chemilithoautotroph. Gel analysis of extracellular proteins revealed no remarkable differences between the wild type and the T2SS mutants. However, enzyme assays revealed that native extracellular alkaline phosphatase is a T2SS substrate, because activity was 10-fold greater for the wild type than a T2SS mutant. In Cme engineered to produce three Ralstonia solanacearum (Rso) exoenzymes, at least 95% of their total activities were extracellular, but unexpectedly high percentages of these exoenzymes remained extracellular in T2SS mutants cultured in rich broth. These conditions appear to permit an alternative secretion process, because neither cell lysis nor periplasmic leakage was observed when Cme produced a Pectobacterium carotovorum exoenzyme, and wild-type Cme cultured in minimal medium secreted 98% of Rso polygalacturonase, but 92% of this exoenzyme remained intracellular in T2SS mutants. We concluded that Cme has a functional T2SS despite lacking any abundan...Continue Reading


Mar 8, 2017·Infection and Immunity·Nicholas P Cianciotto, Richard C White

Related Concepts

Pathologic Cytolysis
Gene Expression Regulation, Bacterial
Bacterial Proteins
Alkalescens-Dispar Group
Outer Membrane
Periplasmic Proteins
Secretory Pathway

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