sentences:  Avian Sarcoma and Leukosis Viruses (ASLV) have ten subgroups (A through J).The envelope glycoprotein of subgroup A is called EnvA and its "env" gene codes for precursor protein known as Pr95.This precursor is cleaved by host cell enzymes to yield the surface protein subunit, gp85, and the transmembrane protein subunit, gp37, which heterodimerize and then form a trimer.