cDNA encoding porin of Neurospora crassa, the major protein component of the outer mitochondrial membrane, was isolated and the nucleotide sequence was determined. The deduced protein sequence consists of 283 amino acids (29,979 daltons) and shows sequence homology of around 43% to yeast porin; however, no significant homology to bacterial porins was apparent. According to secondary structure predictions, mitochondrial porin consists mainly of membrane‐spanning sided beta‐sheets. Porin was efficiently synthesized in vitro from the cDNA; this allowed us to study in detail its import into mitochondria. Thereby, three characteristics of import were defined: (i) import depended on the presence of nucleoside triphosphates; (ii) involvement of a proteinaceous receptor‐like component on the surface of the mitochondria was demonstrated; (iii) insertion into the outer membrane was resolved into at least two distinct steps: specific binding to high‐affinity sites and subsequent assembly to the mature form.

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A cDNA complementary to the mRNA of the ADP/ATP carrier from Neurospora crassa was identified among ordered cDNA clones by hybridizing total polyadenylated RNA to pools of 96 cDNA recombinant plasmids and subsequent cell‐free translation of hybridization‐selected mRNA. Further carrier cDNAs were found by colony filter hybridization at a frequency of 0.2‐0.3%. The gene of the carrier was cloned and isolated on a 4.6‐kbp EcoRI fragment of total Neurospora DNA, and the start of the mRNA was determined by S1 nuclease mapping. From the nucleotide sequence of the cDNA and the genomic DNA, the primary structure of the gene, of the mRNA and of the ADP/ATP carrier protein could be deduced. The gene occurs in a single copy in the genome and related genes are absent. It contains two short introns, and a pyrimidine‐rich promoter region. The mRNA has a 46‐bp 5′ end and a 219‐bp 3′ end. There is an open reading frame coding for the 313 amino acid residues of the Neurospora carrier protein. The amino acid sequence is homologous in 148 positions with the established primary structure of the beef heart carrier.

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For the first time a non natural BMP-variant (EHBMP-2) with osteoinductive properties was produced by expression in E. coli through specific mutation of the amino acid sequence. The substitution of 12 N-terminal amino acids by a nonsense sequence results in a neglectible affinity of EHBMP-2 to the extracellular matrix. In vitro EHBMP-2 induces dose-dependent cartilage formation in neonatal muscle tissue. Single intramuscular implantation in mice results in the formation of an ossicle with functional active bone marrow. The size of the ossicle depends on the amount of implanted EHBMP-2 and can significantly be increased by the combination with a collagen carrier. The largest bone formation is observed after injection of EHBMP-2 containing collagen suspensions. In rats a stronger osteoinductive activity can be achieved by coupling of EHBMP-2 to collagen discs than by coupling natural BMP-2 to the same collagen carrier. Critical size defects in rats' mandibular angels can be restored by the combination of granular collagenous bone matrix (ICBM) with EHBMP-2. Further investigations have to show whether the altered pharmacokinetics of EHBMP-2 has advantages regarding its therapeutical use and tissue-engineering.