A proteomic map of Sulfolobus solfataricus P2, an archaeon that grows optimally at 80 degrees C and pH 3.2, was developed using high-resolution 2-DE and peptide mass fingerprinting. A total of 867 protein spots (659 aqueous Tris-soluble spots and 208 aqueous Tris-insoluble) were mapped over IPG 3-10, 4-7, and 6-11, with second-dimensional gels made of 8-18% polyacrylamide. Three hundred and twenty-four different gene products were represented by the 867 spots, with 274 gene products being identified in the Tris-soluble fractions and 100 gene products in the Tris-insoluble portion. Fifty gene products were found on gels from both fractions. Additionally, an average of 1.50 +/- 0.12 isoforms/protein was identified. This mapping study confirmed the expression of proteins involved in numerous metabolic, transport, energy production, nucleic acid replication, translation, and transcription pathways. Of particular interest, phosphoenolpyruvate carboxykinase (SSO2537) was detected even though the pathway for gluconeogenesis is unknown for this archaeon. Tris-soluble fractions contained many cytosolic proteins while Tris-insoluble fractions contained many membrane-associated proteins, including ABC transporters and an ATP synthase. This study provides an optimized 2-DE approach for investigating the biochemical pathways and post-translational modifications employed by Sulfolobus to survive in its extreme environment.