RNA poly mer ase of gram-pos i tive bac te ria con tains several unique sub units in com par i son to RNA poly mer ase of gram-neg a tive bac te ria. Sigma sub units play a crit i cal role in rec og ni tion of DNA promotor se quence. We fo cused on sigma A fac tor (SigA) from Ba cil lus subtilis. SigA be longs to group 1 transcriptional fac tors. SigA is com posed of four do mains, s 1.1 , s 2 , s 3 , and s 4 that are con nected by flex i ble link ers. SigA is ca pa ble of DNA rec og ni tion

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... h out in ter-ac tion with other part ner, there fore a reg u la tory mech a-nism to pre vent DNA bind ing in in ap pro pri ate times has to ex ist. s 1.1 do main is re spon si ble for auto-reg u la tion of SigA. So lu tion state nu clear mag netic res o nance was used to solve the struc ture of s 1.1. Al though s 1.1 is rel a tively small in size, 9.3 kDa, the res o nance fre quency as sign ment of s 1.1 is not a triv ial task be cause it con tains 23 glutamine or glutamic acid res i dues. As a re sult, one third of amino ac ids have very sim i lar chem i cal shifts and there fore the stan dard set of NMR ex per i ments 2D 1 H-15 N HSQC, 3D HNCA, 3D HN(CO)CA, 3D HNCACB, 3D HN(CO)CACB for se-quen tial res o nance fre quency as sign ment can lead to am-big u ous as sign ment. This prob lem was solved us ing 3D HCCCONH ex per i ments. Side-chain as sign ment was done us ing ad di tional 3D HCCH-TOCSY for ar o matic and aliphatic spec tral re gions and 3D HSQC-TOCSY. We obtained back bone as sign ment for all but two N-ter mi nal res-i dues. Side-chain assignmnent of 97% nu clei was ob tained not in clud ing His-tag. All ex per i ments were per formed on 700 MHz and 850 MHz spec trom e ters. Set of 15N-ed ited 3D HSQC-NOESY ex per i ment and 13C-ed ited 3D HSQC-NOESY ex per i ments for ar o matic and aliphatic spec tral re gions was ac quired to ob tain proton pro ton dis tances from ex per i ments based on nu clear Overhauser ef fect (NOE). The NOESY cross-peak as sign-ment was done us ing pro gram CANDID. 3-bond sca lar cou plings, re sid ual dipolar cou plings, and NOE re strains were uti lized by pro gram CNS to cal cu late the struc ture. There is struc ture of one homologue pro tein from Thermotoga maritima avail able in the PDB da ta base. How ever, even though the sec ond ary struc ture pre dic tion re flects a very sim i lar pat tern, our struc ture of s 1.1 exhibites sig nif i cant dif fer ences in com par i son. In or der to de scribe the in ter nal mo tions of s 1.1 , we ana lysed auto-re lax ation rates R 1 and R 2 , lon gi tu di nal and trans verse cross-cor re lated re lax ation rates, and steady-state Nu clear Overhauser en hance ment. Data was ob tained on 600MHz, 850MHz, and 950MHz spec trom e-ters. Ob tained re lax ation rates were used for spec tral density map ping and model-free anal y sis. This work was sup ported by Czech Sci ence Foun da tion, grant num ber GA 13-16842S.