HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by López-Serrano, D. Articles by Sanchez-Amat, A. Search for Related Content PubMed PubMed Citation Articles by López-Serrano, D. Articles by Sanchez-Amat, A. Agricola Articles by López-Serrano, D. Articles by Sanchez-Amat, A.

Involvement of a novel copper chaperone in tyrosinase activity and melanin synthesis in Marinomonas mediterranea

D. López-Serrano^1,

¹ Department of Biochemistry and Molecular Biology B, University of Murcia, Murcia 30100, Spain
² Department of Genetics and Microbiology, University of Murcia, Murcia 30100, Spain

Correspondence
A. Sanchez-Amat
antonio{at}um.es

Tyrosinase activity and melanin synthesis in the marine bacterium Marinomonas mediterranea in media with very low copper concentrations are dependent on the presence of a protein (PpoB2) that functions as a chaperone to deliver copper to tyrosinase (PpoB1). Under these conditions, mutants in ppoB2 (such as strain T105) produce PpoB1 as an apoenzyme that can be reconstituted to the active holoenzyme by the addition of cupric ions to cell extracts. To study PpoB2 functionality, a system was developed for genetic complementation in M. mediterranea. Using this approach, melanin synthesis was restored in strain T105 when a wild-type copy of ppoB2 was introduced. PpoB2 is a novel protein since it is believed to be the first to be described that contains several motifs similar to metal binding motifs present separately in other types of copper-related protein. At least three motifs, a His-rich N-terminal region, and the short CxxxC and MxxxMM sequences, are essential for the functionality of PpoB2, since site-directed mutagenesis of these motifs resulted in a non-functional protein. In addition, it was demonstrated that PpoB2 is a membrane copper transporter putatively participating in the delivery of this ion specifically to the tyrosinase of M. mediterranea and not to a second copper oxidase showing laccase activity that this micro-organism also expresses. PpoB2 has similarities with the COG5486 group encoding putative transmembrane metal binding proteins, and is believed to be the first protein in this group to be experimentally characterized. It may constitute the first example of a novel type of protein involved in copper trafficking in bacteria.

Present address: Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.