Complete sequential assignment and secondary structure prediction of the cannulae forming protein CanA from the hyperthermophilic archaeon Pyrodictium abyssi

CanA from Pyrodictium abyssi forms a heat-resistant organic hollow-fiber network together with CanB and CanC. An N-terminally truncated construct of CanA (K(1)-CanA) gave NMR spectra of good quality that could be assigned by three-dimensional NMR methods on (15)N and (13)C–(15)N enriched protein. We assigned the chemical shifts of 96% of all backbone (1)H(N) atoms, 98% of all backbone (15)N atoms, 100% of all (13)C(α) atoms, 100% of all (1)H(α) atoms, 90% of all (13)C′ atoms, and 100% of the (13)C(β) atoms. Two short helices and 10 β-strands are estimated from an analysis of the chemical shifts leading to a secondary structure content of K(1)-CanA of 6% helices, 44% β-pleated sheets, and 50% coils.