Gene structure of the P100 serine-protease component of the human Ra-reactive factor

The Ra-reactive factor (RaRF) is a complement-dependent anti-microbial fact or that reacts with numerous microorganisms such as viruses, bacteria, fung i and protozoa. It is a complex of a mannan-binding lectin (MBL) and the se rine protease, P100 (MASP1). P100 activates the C4 component of the complem ent system and its domain organization is similar to C1r and C1s. In this s tudy, determination was made of the structure of the human P100 gene which was found longer than 67 kbp and to be comprised of 16 exons. Its non-prote ase region consisted of 10 exons, as in the case of C1r and C1s, and the in trons were found present in the boundary separating two CUB domains, an EGF -like domain and two CCP domains and each CUB and CCP domain contained extr a internal introns. The serine protease region was comprised of 6 exons in contrast to C1r and C1s, either of which consists of a single exon. The exo n-intron structure was found to reflect the evolution of these molecules an d P100 to have derived earlier in the stage of evolution than C1r or C1s. ( C) 1999 Published by Elsevier Science Ltd. All rights reserved.