Porins from plants. Molecular cloning and functional characterization of two new members of the porin family

J Biol Chem. 1994 Oct 14;269(41):25754-60.

Abstract

Porins are voltage-gated diffusion pores found in all eukaryotic kingdoms. Here we describe, for the first time, the identification and characterization of two cDNAs encoding porins from plants. Peptide sequences obtained from a 30-kDa protein of envelope membranes from pea root plastids allowed the isolation of two cDNA clones from pea and maize. On the protein level, both proteins are homologous by 58%. Sequence comparison against the Swiss-Prot sequence data base revealed a homology of about 25% to mitochondrial porins from fungi and human. Computer-aided predictions of the secondary structure of the plant porins revealed the presence of 16 antiparallel beta-strands that are also found in mitochondrial porins. Porins from non-green plastids and from the outer mitochondrial membrane were reconstituted into planar lipid bilayers. The proteins showed high pore-forming activities and similar single-channel conductances. In vitro translated porin was preferentially imported only into non-green plastids but not into chloroplasts. To our knowledge, this is the first example of selective import of a plastid protein into different types of plastids. This finding is in line with the observation that an immunoreactive 30-kDa band was only found in non-green plastids and mitochondria but not in chloroplasts. We conclude that mitochondria and non-green plastids possess homologous porin proteins, whereas chloroplasts are characterized by a different type of porin.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Biological Transport
  • Biomarkers
  • Cell Compartmentation
  • Cell Fractionation
  • Cloning, Molecular
  • DNA, Complementary / genetics
  • Genes, Plant / genetics*
  • Intracellular Membranes*
  • Ion Channels / classification
  • Ion Channels / genetics*
  • Ion Channels / isolation & purification
  • Ion Channels / metabolism
  • Lipid Bilayers / metabolism
  • Mitochondria
  • Molecular Sequence Data
  • Multigene Family
  • Pisum sativum
  • Plant Proteins / classification
  • Plant Proteins / genetics*
  • Plant Proteins / isolation & purification
  • Plant Proteins / metabolism
  • Plant Roots
  • Plastids*
  • Porins / genetics*
  • Porins / isolation & purification
  • Porins / metabolism
  • Protein Biosynthesis
  • Protein Structure, Secondary
  • Sequence Analysis
  • Sequence Homology, Amino Acid
  • Vegetables / genetics*
  • Zea mays

Substances

  • Biomarkers
  • DNA, Complementary
  • Ion Channels
  • Lipid Bilayers
  • Plant Proteins
  • Porins
  • por1 protein, Zea mays
  • pspor1 protein, Pisum sativum

Associated data

  • GENBANK/X73429
  • GENBANK/Z25540