Cucumber basic blue protein function

Cucumber basic blue protein (Cbp) is a protein without known function, also known as cusacyanin or plantacyanin. Its structure (Guss et al., 1988) completes the repertoire of cupredoxins with known structures. The topology of its folding is similar (Fig. 5) to those of plastocyanin and azurin, as might have been expected from sequence similarities and... 

The type I copper sites function as electron transfer centers in the blue copper proteins and in multicopper enzymes, particularly oxidases (33). They are characterized by their intense blue color, their unusually small A values, and their very positive redox potentials (Table II). X-ray crystal structures of several blue copper proteins have been determined, notably plastocyanin (34), azurin (35), cucumber basic blue protein (36), and pseudoazurin (37). The active site structures show marked similarities but also distinct differences (Fig. 8). 

Basic blue proteins have been isolated from a number of plant sources and have previously been referred to as plantacyanin (Aikazyan and Nalbandyan, 1975,1979 Sakurai et al, 1982). The protein from cucumber has been the most extensively studied of the basic blue proteins and the crystal structure is now available (Guss et al., 1988). The function of this basic blue protein is unknown, however, it is probably not involved in photosynthetic electron transport as it will not replace plastocyanin in that electron transport chain (Adman, 1985). 

The physiological functions of the phytocyanins are also currently unknown. This family of proteins consists of stellacyanin (20 kD) [97, 101], umecyanin (14 kD), the basic blue protein (from cucumber = plantacyanin) (8 kD), and cusacyanin (molecular masses see [17]). 

Blue copper proteins, 36 323, 377-378, see also Azurin Plastocyanin active site protonations, 36 396-398 charge, 36 398-401 classification, 36 378-379 comparison with rubredoxin, 36 404 coordinated amino acid spacing, 36 399 cucumber basic protein, 36 390 electron transfer routes, 36 403-404 electron transport, 36 378 EXAFS studies, 36 390-391 functional role, 36 382-383 occurrence, 36 379-382 properties, 36 380 pseudoazurin, 36 389-390 reduction potentials, 36 393-396 self-exchange rate constants, 36 401-403 UV-VIS spectra, 36 391-393 Blue species... 

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