Role of mitochondrial carrier protein Mrs3/4 in iron acquisition and oxidative stress resistance of Cryptococcus neoformans

Med Mycol. 2002 Dec;40(6):581-91. doi: 10.1080/mmy.40.6.581.591.


Cryptococcus neoformans is a pathogenic basidiomycete that causes meningitis in immunocompromised patients. In this paper, we demonstrate that a previously described oxidant-sensitive mutant, oxy1, has constitutive ferric reductase and iron uptake, similar to a ferric reductase regulatory mutant, frr1. Through meiotic genetic analysis, we show that the two mutations are allelic. By complementation of frr1 with a genomic library, we isolated a gene, MRS3/4. The encoded protein is a putative solute transporter of the inner mitochondrial membrane. Disruption of this gene led to high ferric reductase, iron uptake and iron content, as well as increased sensitivity to hydrogen peroxide and slow growth in low iron medium. The disrupted gene is allelic with oxy1 and frr1. We sequenced the oxy1 and frr1 alleles of MRS3/4 and found that the frr1 mutation results in a premature stop codon, while the oxy1 mutation results in the substitution of a highly conserved glutamate residue with lysine. The Mrs3/4 protein appears to be involved in mitochondrial iron transport in eukaryotes. Resistance to strong oxidants requires stringent control of iron metabolism.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cation Transport Proteins*
  • Cryptococcus neoformans / genetics
  • Cryptococcus neoformans / metabolism*
  • Cryptococcus neoformans / physiology
  • FMN Reductase / genetics
  • FMN Reductase / metabolism
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Deletion
  • Gene Expression Regulation, Fungal
  • Iron / metabolism*
  • Mitochondria / metabolism*
  • Mitochondrial Proteins
  • Molecular Sequence Data
  • Oxidative Stress / physiology*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism
  • Sequence Analysis, DNA


  • Carrier Proteins
  • Cation Transport Proteins
  • Fungal Proteins
  • MRS3 protein, S cerevisiae
  • MRS4 protein, S cerevisiae
  • Mitochondrial Proteins
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • Iron
  • FMN Reductase
  • ferric citrate iron reductase

Associated data

  • GENBANK/AY048991