Your code is not valid.
Code:
redirect 301 store http://www.site2.com/store
This code redirects URL's like
http://www.site1.com/store/this_url to
http://www.site2.com/store/this_url.
Code:
RewriteEngine on
RewriteRule ^store(.*)$ http://www.site2.com/store/ [L,R=301]
This code redirects URL's like
http://www.site1.com/store/this_url to
http://www.site2.com/store/.
Place this
.htaccess file in the home directory of site1.com.
Jean-Luc