Consider: [AG]-x-C-x(4)-{DE}. This pattern is translated as: Ala or Gly, any, Cys, any, any, any, any, anything but Glu or Asp.

Pattern rules:

• A single amino acid character designates that only that amino acid can be allowed in that position! For example: D-A will match the two amino acids Glu and Ala in sequence!
• A group within [ and ] designates a positive group where any of the amino acids within [...] will be allowed in a position! For example [AG] will allow Ala or Gly in a single position!
• A group within { and } designates a negative group where none of the amino acids within {...} will be allowed in a position! For example {DE} will allow anthing but Glu or Asp!
• The x character designates that any amino acid can be matched within a single position!
• A repetition group is written using the ( and ) characters and can contain a single number, for example ...-D(4)-.. which corresponds to four repetitions of Glu. A repetition group may also be a range, for example ...-x(0,3)-... which matches anything between nothing at all and three amino acids of any kind!
• Each group or amino acid should be delimited by the - character