Secretion of a human collagen alpha 1(I) chain fragment was achieved in Hansenula polymorpha using the native alpha 1(I) procollagen secretory signal sequence. The N-terminal propeptide in the fragment was cleaved off during secretion, yielding the N-terminus of mature alpha 1(I) collagen. In Pichia pastoris transformants, the expression of the fragment could be detected on RNA-level, but the product could not be determined extracellularly. After fusion of the fragment with a myc-HIS6 epitope, the intact product was found intracellularly. The difference in the extracellular level of the protein between the two expression hosts is most likely caused by difference in secretion efficiency. (C) 2000 Elsevier Science Inc. All rights reserved.