Protein and gene structure of a chlorocruorin chain of Eudistylia vancouverii

The polychaete annelid, Eudistylia vancouverii, contains as oxygen carrier a hexagonal bilayer (HBL) chlorocruorin. One of the globin chains, chain a1 , has 142 amino acids (Mr 16,054.99) and its sequence deviates strongly fro m other nonvertebrate globin sequences. Unprecedented, it displays a Phe at the distal position E7 as well as at position B10, creating a very hydroph obic heme pocket probably responsible for the low oxygen affinity of the na tive molecule. Phylogenetic analysis of annelid globin chains clearly prove s that globin chain al belongs to type I of globin chains having a pattern of 3 cysteine residues essential for the aggregation into a HBL structure. The gene coding for globin chain al is interrupted by 2 introns at the cons erved positions B12.2 and G7.0. Based on protein and gene structure it can therefore be concluded that the globin chains of chlorocruorins are not fun damentally different from other annelid globin chains. (C) 2001 Academic Pr ess.