Binding of trans-acting protein AngCP to the CCAAT-containing motifs in Aspergillus niger glaA promoter

CCAAT-binding proteins AngCPl and AngCP2 of Aspergillus niger binding to DC (-489 - -414 bp) and PC (-390 - -345 bp) of A. niger glaA gene were respectively purified by 20% - 40% saturated ammonium sulfate, gel filtration, Heparin SepharoseCl-6B chromatography and DNA sequence-specific affinity chromatography. Gel filtration and SDS-PAGE revealed that both AngCPl and AngCP2 were of 120 kD, comprised of two subunits of 34 kD and 50 kD. Western blot showed that the 34 kD subunits of both AngCPl and AngCP2 cross-reacted specifically with the anti-AngHAPC antiserum. Further electrophoretic mobility shift assay identified that AngCPl and AngCP2 were the same protein, designated AngCP. Southwestern blot showed that the affinity of the 34 kD sub-unit to DC was stronger than that of the 50 kD subunit to PC. These results suggested that interaction between AngCP, DC and PC plays an important role in the regulation of transcription of Aspergillus niger glaA gene.