Myoglobin-like aerotaxis transducers in Archaea and Bacteria

Haem-containing proteins such as haemoglobin and myoglobin play an essentia l role in oxygen transport and storage. Comparison of the amino-acid sequen ces of globins from Bacteria and Eukarya suggests that they share an early common ancestor, even though the proteins perform different functions in th ese two kingdoms(1-6). Until now, no members of the globin family have been found in the third kingdom, Archaea. Recent studies of biological signalli ng in the Bacteria and Eukarya have revealed a new class of haem-containing proteins that serve as sensors(7). Until now, no haem-based sensor has bee n described in the Archaea. Here we report the first myoglobin-like, haem-c ontaining protein in the Archaea, and the first haem-based aerotactic trans ducer in the Bacteria (termed HemAT-Hs for the archaeon Halobacterium salin arum, and HemAT-Bs for Bacillus subtilis). These proteins exhibit spectral properties similar to those of myoglobin and trigger aerotactic responses.