Eukaryotic Cell doi:10.1128/EC.00345-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Pneumocystis Encodes a Functional S-Adenosylmethionine Synthetase Gene
Geetha Kutty,
Beatriz Hernandez-Novoa,
Meggan Czapiga,
and
Joseph A. Kovacs*
Critical Care Medicine Department, NIH Clinical Center, National Institutes of Health, Bethesda, MD, USA; Research Technologies Branch, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
* To whom correspondence should be addressed. Email:
jkovacs{at}nih.gov.
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Abstract |
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S-Adenosylmethionine (AdoMet) synthetase (EC 2.5.1.6) is the enzyme that catalyzes the synthesis of S-adenosylmethionine, an important molecule for all cellular organisms. We have cloned and characterized an AdoMet synthetase gene (sam1) from Pneumocystis. This gene is transcribed primarily as an 
1.3 kb mRNA which encodes a protein containing 381 amino acids in Pneumocystis carinii or P. murina and 382 amino acids in P. jirovecii. sam1 was also transcribed as part of an apparent polycistronic transcript of 5.6 kb, together with a putative chromatin remodeling protein homologous to yeast CHD1. Recombinant Sam1 when expressed in E. coli showed functional enzyme activity. Immunoprecipitation and confocal immunofluorescence analysis using an anti-peptide antibody showed that this enzyme is expressed in P. murina. Thus, Pneumocystis, like other organisms, can synthesize its own AdoMet and may not depend on its host for the supply of this important molecule.
