Figure 1

Example calculation of the weight scores of domains. Black lines represent protein sequences and the colored boxes, circles, and diamonds represent different domains. The number of occurrences of two exemplary domains, A and B, is three (P1, P2, and P3), and the number of distinct partner domains of A and B is three (E, D, and A) and one (E), respectively. The IAF scores of A and B are 0.125, and the IV scores of A and B are 0.3 and 1.0, respectively. We can obtain the final weight score of domain A (0.038) and domain B (0.125) from the IDF and IV scores. From the weight scores of the two domains, we can determine that domain A is a more promiscuous domain than domain B.