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The structural role of the zinc ion can be dispensable in prokaryotic zinc-finger domains.

Abstract：

:The recent characterization of the prokaryotic Cys(2)His(2) zinc-finger domain, identified in Ros protein from Agrobacterium tumefaciens, has demonstrated that, although possessing a similar zinc coordination sphere, this domain is structurally very different from its eukaryotic counterpart. A search in the databases has identified approximately 300 homologues with a high sequence identity to the Ros protein, including the amino acids that form the extensive hydrophobic core in Ros. Surprisingly, the Cys(2)His(2) zinc coordination sphere is generally poorly conserved in the Ros homologues, raising the question of whether the zinc ion is always preserved in these proteins. Here, we present a functional and structural study of a point mutant of Ros protein, Ros(56-142)C82D, in which the second coordinating cysteine is replaced by an aspartate, 5 previously-uncharacterized representative Ros homologues from Mesorhizobium loti, and 2 mutants of the homologues. Our results indicate that the prokaryotic zinc-finger domain, which in Ros protein tetrahedrally coordinates Zn(II) through the typical Cys(2)His(2) coordination, in Ros homologues can either exploit a CysAspHis(2) coordination sphere, previously never described in DNA binding zinc finger domains to our knowledge, or lose the metal, while still preserving the DNA-binding activity. We demonstrate that this class of prokaryotic zinc-finger domains is structurally very adaptable, and surprisingly single mutations can transform a zinc-binding domain into a nonzinc-binding domain and vice versa, without affecting the DNA-binding ability. In light of our findings an evolutionary link between the prokaryotic and eukaryotic zinc-finger domains, based on bacteria-to-eukaryota horizontal gene transfer, is discussed.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Baglivo I,Russo L,Esposito S,Malgieri G,Renda M,Salluzzo A,Di Blasio B,Isernia C,Fattorusso R,Pedone PV

doi

10.1073/pnas.0810003106

subject

Has Abstract

pub_date

2009-04-28 00:00:00

pages

6933-8

issue

eissn

0027-8424

issn

1091-6490

pii

0810003106

journal_volume

106

pub_type

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The structural role of the zinc ion can be dispensable in prokaryotic zinc-finger domains.