first cyclin box found in cyclin-H (CCNH) and similar proteins
CCNH, also called MO15-associated protein, p34, or p37, is normally associated with the cyclin-dependent kinase cdk7, the catalytic subunit of the CDK-activating kinase (CAK) enzymatic complex. CCNH contains two cyclin boxes. This model corresponds to the first one. The cyclin box is a protein binding domain.