3-10-15 Update
Working N-Glycosylation Site RegEx:
import re
p = re.compile(ur'N[^X][ST]')
test_str = u"MGRFSSLCALTAVIHSFGRVSAAIGPVTDLTISNADVSPDGFTRAAVLANGVFPGPLITGNKGDNFQINVIDNLSNETMLKSTSIHWHGFFQKGTNWADGAAFVNQCPIATGNSFLYDFTATDQAGTFWYHSHLSTQYCDGLRGPMVVYDPSDPHADLYDVDDETTIITLSDWYHTAASLGAAFPIGSDSTLINGLGRFAGGDSTDLAVITVEQGKRYRMRLLSLSCDPNYVFSIDGHNMTIIEADAVNHEPLTVDSIQIYAGQRYSFVLTADQDIDNYFIRALPSAGTTSFDGGINSAILRYSGASEVDPTTTETTSVLPLDEANLVPLDSPAAPGDPNIGGVDYALNLDFNFDGTNFFINDVSFVSPTVPVLLQILSGTTSAADLLPSGSLFALPSNSTIEISFPITATNAPGAPHPFHLHGHTFSIVRTAGSTDTNFVNPVRRDVVNTGTAGDNVTIRFTTDNPGPWFLHCHIDFHLEAGFAIVFSEDTADVSNTTTPSTAWEDLCPTYNALDSSDL"
re.findall(p, test_str)