COMPETENCE AND VIRULENCE OF STREPTOCOCCUS-PNEUMONIAE - ADC AND PSAA MUTANTS EXHIBIT A REQUIREMENT FOR ZN AND MN RESULTING FROM INACTIVATIONOF PUTATIVE ABC METAL PERMEASES

The adcCBA putative operon of Streptococcus pneumoniae, an important h uman pathogen, was identified in a search for transformation-deficient mutants. It was found to exhibit homology to ATP-binding cassette (AB C) transport operons encoding streptococcal adhesins such as FimA of S treptococcus parasanguis and PsaA of S, pneumoniae, The latter was rec ently shown to be essential for virulence as judged by intranasal or i ntraperitoneal challenge of mice, We suggested previously that AdcA, t ogether with a set of 14 proteins, including PsaA and homologous adhes ins, defines a new family of external solute-binding proteins specific for metals, In this work, Northern analysis revealed the existence of two adcB-adcA specific transcripts originating within adcC or further upstream, consistent with the hypothesis that ade is an operon, Inves tigation of growth of ade and psaA mutants in synthetic medium reveale d that the addition of Zn improved the growth rate of the former, wher eas the latter exhibited an absolute requirement for added Mn, A psaA- adc double mutant turned out to be essentially non-viable unless both metals were added in the appropriate ratio. Taken together, these resu lts suggest a previously undocumented requirement of S. pneumoniae for Zn and Mn, The addition of Zn also restored near-normal spontaneous t ransformation of ade mutant cells in standard transformation medium. Z n was found to be specifically required soon after contact of cells wi th the competence-stimulating peptide, revealing an unsuspected need f or Zn in transformation of S, pneumoniae, The removal of Mn from stand ard transformation medium also resulted in transformation deficiency o f psaA mutant cells. Taken together, these results lead us to propose that Adc is an ABC-type Zn permease, the first such protein complex id entified in any organism, and that Psa ia an ABC-type Mn permease comp lex.