EXPRESSION OF THE LONG ARM SEQUENCE OF MOUSE LAMININ ALPHA-1, BETA-1,OR GAMMA-1 CHAIN IN COS1 CELLS AND ASSEMBLY OF MONKEY-MOUSE HYBRID LAMININ

Mouse laminin alpha 1, beta 1, gamma 1 sequence covering truncated reg ions of the long arm was transiently expressed in monkey COS1 cells, U nlike natural laminins, in which only alpha beta gamma trimers are sel ectively assembled and disulfide-bonded at the long arm, a large fract ion of mouse chains formed disulfide-bonded homopolymers, However, a s mall fraction of mouse beta 1 (or gamma 1) formed hybrid beta 1 gamma 1 dimers with endogenous monkey gamma 1 (or beta 1), These hybrid beta 1 gamma 1 dimers formed alpha 1 beta 1 gamma 1 trimer with monkey alp ha 1. Mouse alpha 1 also formed disulfide bonds with monkey beta 1 gam ma 1 dimer, Thus, a common mechanism is shared by laminin chains of di fferent animal origins, Sequences in the E8 region at the C-terminal e nd of the long arm were crucial for this chain-selective assembly, Whe n the C-terminal sequence of mouse beta 1 long arm was extended beyond the alpha-loop, the hybrid trimer formation was diminished, This supp orted the model of altered chain arrangement around the alpha-loop.