The phycobiliprotein beta 16.2 of the allophycocyanin core from the cyanobacterium Mastigocladus laminosus. Characterization and complete amino-acid sequence.

The minor phycobiliprotein beta 16.2 was isolated from the APC-core of phycobilisomes from the cyanobacterium Mastigocladus laminosus. Its complete amino-acid sequence and some spectral characteristics are presented. beta 16.2 consists of 169 amino acids and its molecular mass is 19,390 Da. A phycocyanobilin chromophore is covalently bound to a cysteine at position 84 as in all other phycobiliproteins. The first 138 amino acids are highly homologous to the N-terminal part of beta AP (62.5%), whereas the C-terminal part has no homology. The absorption maximum is situated at 624 nm, the fluorescence emission maximum at 644 nm in phosphate buffer, pH 7.0. Both values are slightly redshifted compared with alpha AP and beta AP.