Fungal Laccases, Ascorbate Oxidases, and Related Proteins

Fungal Laccases, Ascorbate Oxidases, and Related Proteins 

Structurally Based Amino-Acid Sequence Alignment of Fungal Laccases, Ascorbate Oxidases, and Related Proteins  

Similarity Matrix for the Amino-Acid Sequence Alignment Displayed in Table IV  

Evolution of the Blue Oxidases and Related Proteins from a Common Ancestor 

The similarity matrix calculated in Messerschmidt and Huber (202) indicates clearly the six-domain structure of ceruloplasmin and three-domain structures for laccase and ascorbate oxidase. The internal triplication within the ceruloplasmin amino-acid sequence is reflected by values of about 60% difference. Comparison of both the N-terminal domains and the C-terminal domains of the blue oxidases indicates, respectively, a relationship that is closer and relevant values for percent difference that are significantly lower than those for other comparisons. This might reflect the requirements for the trinuclear copper site. The lowest values of about 70 to 73% difference are observed for both N-terminal and C-terminal domains of laccase and ascorbate oxidase, showing that the two oxidases are more closely related to ceruloplasmin than either of them. 

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Table V supplies insight into the relatedness within fungal laccases and ascorbate oxidases and to the other included proteins. Obviously both Tables Va and Vb show the same trend. The laccases of the narrowly related basiodomycetes P. radiata and C. hirsutus show differences of only 37%. The differences for the laccases from the ascomycetes N. crassa and C. parasitica are about 50%. The laccase of the deuteromy-cete A. nidulans shows very low identities to all partners of the alignment when all residues are included into the calculations (Table Va). The picture becomes clearer when badly aligning segments are omitted from the calculations (Table Vb). The differences from the other lac-...

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