Structure of Jann 2411

¶ … structure of Jann_2411( DUF14790) from Jannaschia sp at 1.45 A resolution reveals a new fold ( the ABATE domain) and suggests its possible role as transcription regulator"

The purpose of this study was to resolve the structure of the protein Jann_2411 and relate its structure to the functional properties of the protein. The researchers determined the structure using the method of x-ray crystallography (multiple wavelength anomalous diffraction) and structural analysis of the protein revealed it to be a putative stress-related transcription factor.

Jann_2411 has a molecular weight of 20.7 kDa (residues 1-187) and a calculated isoelectric point of 6.6 and its crystal structure was determined using the semiautomated high-throughput pipeline of the Joint Center for Structural Genomics. Structural analysis revealed a two domain organization with the N-terminal domain consisting of a new fold called ABATE (Alpha-beta hairpin and Alpha TandEm) domain and the C-terminal domain forming a treble-clef zinc finger after a characteristic conserved sequence. Jan_2411 forms a dimer that binds DNA forming a putative stress-related transcription factor for which the ABATE domain is implicated.

Jann_2411 belongs to the Pfam family known as DUF1470, which accounts for the entire length of the protein sequence. However, the structure shows that Jann_2411 is actually comprised of two domains. The first domain (residues 1 -- 142) can be visualized as two subdomains (H2 -- H4, 1 -- 2 and H5 -- H7, 3 -- 4) that share similar topology and secondary-structure elements, namely a helix -- -hairpin -- helix motif (H2-1-2-H3 in the first subdomain; H6-3- 4-H7 in the second subdomain), with an additional helix (H4 from the first subdomain and H5 from the second subdomain) linking the two motifs. The researchers have therefore named this region the ABATE domain, representing the Alpha-Beta-hairpin-Alpha TandEm motif.

The second domain (residues 143 -- 187; H8, 5 -- 6, H9) forms a treble-clef zinc finger. The zinc ion is coordinated by two cysteines (Cys147 and Cys152) from a loop termed the zinc knuckle, located between the strands of the third -hairpin (5 -- 6), and two cysteines from the N-terminus of helix H9 (Cys168 and Cys172). This arrangement of zinc-coordinating residues is typical of treble-clef zinc fingers. Other strictly conserved residues in this domain include Asp158 and Arg175. A high degree of conservation is observed for a number of positively charged residues (Arg143, Arg161, Arg165, Lys177, Arg182 and Arg184), suggesting that this region could present a nucleic acid binding site. Furthermore, residues 146 (a hydrophobic residue) and 167 (an aromatic residue) are highly conserved and could intercalate between the DNA bases. Based on the most conserved motif found in the C-terminal -helix in this family of proteins, we have named this domain the CGNR zinc finger. The actual amino-acid sequence in Jann_2411 is CQNR.

The dimer exists in quarternary form. Treble-clef zinc fingers are usually incorporated into larger structures and are found in proteins with a wide range of functions, many of which involve transcriptional regulation. Genes predicted to have functional associations with Jann_2411 in the STRING database (http://string.embl.de) include a transmembrane protein of unknown function (Jann_2410) and the transcriptional regulator Jann_2412, a member of the Asr gene family. The Asr gene family is widespread in higher plants and most members of this family are up-regulated under a range of environmental stress conditions; their products are thought to function as transcriptional regulators.