Five hundred transformants were further screened and all found to express ampicillin resistance.

Minimum DNA length for Imu3 binding The minimum length of single-stranded DNA required for Imu3 binding was studied by initially saturating Imu3 with short DNA fragments of known lengths. The reaction mixtures of Imu3 (10 μg) and an at least 5-fold excess of oligonucleotides, were incubated for 30 min at 37°C (allowing Imu3 to bind to oligonucleotides of sufficient length) prior to the addition PXD101 mw of the indicator DNA (100 ng pUC19/EcoRI). Oligonucleotides too short to form a complex with Imu3, bind to the indicator DNA provoking an electro-mobility shift. Samples were incubated for another 30 min at 37°C, to allow potential binding of Imu3 to the indicator DNA. The samples were later resolved on 0.8% agarose Tris-borate gels. The short DNA fragments were all synthesised as single-stranded oligonucleotides, the sequences of which are given in Table  2. Table 2 Oligonucleotide sequences used to determine the minimal length of single-stranded and double-stranded DNA for DNA–Imu3 complex formation Oligonucleotide 5′-3′ sequence gCc 6-mer (M13) gCggTTcv 67 7-mer (M13) gCggTTC 63 8-mer (M13) TggCggTT 63 9-mer (M13) gTggCggTT 67 10-mer (M13) ggTggCggTT 70 11-mer (M13) ggTggCggTTC 73 12-mer (M13) AgggTggCggTT 67 13-mer (M13) gAgggTggCggTT 69 14-mer (M13) gAgggTggCggTTC 71 15-mer

(M13) gAgggTggCggTTCT 67 15-TATA (poly AT) TATATATATATATAT 0 15-gCgC (poly GC) gCgCgCgCgCgCgCg SB203580 molecular weight 100 The

lengths of the oligonucleotides spanned from 6 to 32 nucleotides. Acknowledgements This work was financed by the Slovene Research Agency (ARRS). We would Morin Hydrate like to thank Dušan Žigon for help with mass spectroscopy, Nataša Poklar Ulrih with DNA melting experiments and Luka Ausec for assistance with bioinformatics issues. Electronic supplementary material Additional file 1: Figure S1: Effect of His-tag presence on Imu3 DNA-binding ability. M: PageRuler Prestained Protein Ladder (Fermentas); 1. Imu3 with His-tag (SDS-PAGE); 2. Imu3 with His-tag removed (SDS-PAGE); 3. 100 ng of pUC19/EcoRI (agarose electrophoresis, AE); 4. 100 ng of pUC19/EcoRI complexed with Imu3 with His-tag removed (AE). (JPEG 959 KB) Additional file 2: Figure S2: Dimerisation of Imu3 and USP proteins, 10% SDS PAGE gel. M: PageRuler Prestained Protein Ladder (Fermentas); 1. Imu3 protein (11.5 kDa); 2. USP protein (67 kDa). Samples following cross-linking with glutaraldehyde (3-7); 3. Imu3 protein, 4. USP protein, 5. Imu3 and USP, 6. Imu3 and USP with addition of DNA, 7. LexA protein mono/dimer (24/48 kDa). (TIFF 5 MB) Additional file 3: Figure S3: Representative electromobility shift assays on 0.8% agarose gels. Effects of pH, NaCl and temperature on DNA–Imu3 complex relaxation. Lane 1: pUC19/EcoRI DNA (100 ng); lane 2: Imu3-pUC19/EcoRI untreated complex; lanes 3-7: Imu3-pUC19/EcoRI complex treated with pH values 10, 11, 12, 12.