KINESIN LIGHT-CHAIN IN A EUBACTERIUM

A eubacterial homolog of a kinesin light chain gene has been isolated and characterized from the cyanobacterium Plectonema boryanum. Althoug h the eubacterial and eukaryotic kinesin light chains are highly simil ar in amino acid sequence, the eubacterial sequence differs in several distinguishing structural features, including the absence of a putati ve PEST domain and the presence of additional highly conserved imperfe ct tandem repeats. Two soluble kinesin light chain antigens have been identified from whole-cell lysates by immunoblot analysis, Attempts to identify a canonical kinesin heavy-chain gene or protein were unsucce ssful, suggesting that a kinesin heavy chain may be absent or unnecess ary for kinesin light-chain function in this eubacterium. Our findings establish that certain basal elements of eukaryotic cellular transpor t appear to be resident in eubacteria. We discuss the possibility that the eukaryotic kinesin light chain was acquired by lateral gene trans fer.