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J. Bacteriol., 02 1997, 853-862, Vol 179, No. 3
ML Montesinos, A Herrero and E Flores
The activities of uptake of thirteen 14C-labeled amino acids were
determined in nine cyanobacteria, including the unicellular strains
Synechococcus sp. strain PCC 7942 and Synechocystis sp. strain PCC 6803;
the filamentous strain Pseudanabaena sp. strain PCC 6903, and the
filamentous, heterocyst-forming strains Anabaena sp. strains PCC 7120 and
PCC 7937; Nostoc sp. strains PCC 7413 and PCC 7107; Calothrix sp. strain
PCC 7601 (which is a mutant unable to develop heterocysts); and Fischerella
muscicola UTEX 1829. Amino acid transport mutants, selected as mutants
resistant to some amino acid analogs, were isolated from the Anabaena,
Nostoc, Calothrix, and Pseudanabaena strains. All of the tested
cyanobacteria bear at least a neutral amino acid transport system, and some
strains also bear transport systems specific for basic or acidic amino
acids. Two genes, natA and natB, encoding elements (conserved component,
NatA, and periplasmic binding protein, NatB) of an ABC-type permease for
neutral amino acids were identified by insertional mutagenesis of strain
PCC 6803 open reading frames from the recently published genomic DNA
sequence of this cyanobacterium. DNA sequences homologous to natA and natB
from strain PCC 6803 were detected by hybridization in eight cyanobacterial
strains tested. Mutants unable to transport neutral amino acids, including
natA and natB insertional mutants, accumulated in the extracellular medium
a set of amino acids that always included Ala, Val, Phe, Ile, and Leu. A
general role for a cyanobacterial neutral amino acid permease in recapture
of hydrophobic amino acids leaked from the cells is suggested.
Copyright © 1997, American Society for Microbiology
Amino acid transport in taxonomically diverse cyanobacteria and identification of two genes encoding elements of a neutral amino acid permease putatively involved in recapture of leaked hydrophobic amino acids
Instituto de Bioquimica Vegetal y Fotosintesis, Universidad de Sevilla- Consejo Superior de Investigaciones Cientificas, Spain.
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