Such
regulations, restrictions, and boundaries may from time to time be
amended, supplemented, changed, modified or repealed. In case, however,
of a protest against such change duly signed and acknowledged by the
owners of thirty percent (30%) or more, either of the areas of the
land (exclusive of streets and alleys) included in such proposed change
or within an area determined by lines drawn parallel to and one hundred
eighty-five (185) feet distant from the boundaries of the district
proposed to be changed, such amendment shall not become effective
except by the favorable vote of two-thirds (⅔) of all the members
of the legislative body of such municipality. The provisions of Section
89.050, RSMo., relative to public hearing and official notice shall
apply equally to all changes or amendments.