Xenopus laevis gelatinase B (Xmmp-9): development, regeneration, and wound healing.

It has been argued that matrix metalloproteinases play important roles in cellular differentiation and regeneration in certain systems. While studying changes in gene expression associated with the phenomena of cornea/lens transdifferentiation ("lens regeneration"), which takes place in the larva of Xenopus laevis, we identified the Xenopus gelatinase B gene. The open reading frame is homologous to other gelatinase B genes identified in other species and encodes all of the domains characteristic of this protein. Xenopus gelatinase B (Xmmp-9) is first expressed during early tail-bud stages in a subset of mesodermal cells scattered throughout the body. Expression is also seen in the peripheral tissues of the developing liver diverticulum, the hindgut/cloaca, and the paired caudal vein, and its dorsal branch in the larval tail. Given the significant role of matrix metalloproteinases in degrading components of the extracellular matrix, Xmmp-9 expression may be important in the morphogenesis of these structures. Xmmp-9 expression was also examined during the processes of cornea/lens transdifferentiation, epithelial wound healing, and limb regeneration in Xenopus larvae. Although Xmmp-9 is expressed very early during cornea/lens transdifferentiation, expression is restricted to the site of the peripheral wound created by removal of the original lens, which triggers transdifferentiation. Expression was not found in the central, uninjured area of the cornea where transdifferentiation takes place. Therefore, Xmmp-9 does not appear to play an important role in cornea/lens transdifferentiation. Xmmp-9 expression is associated with other epithelial wounds, indicating that gelatinase B is expressed in the general context of wound healing in Xenopus. Finally, Xmmp-9 is expressed in the ectoderm and mesoderm at the tip of the amputated limb, very early during limb regeneration, where it is argued to play a role in this process.

The apeE gene of Salmonella typhimurium encodes an outer membrane esterase not present in Escherichia coli.

Salmonella typhimurium apeR mutations lead to overproduction of an outer membrane-associated N-acetyl phenylalanine beta-naphthyl ester-cleaving esterase that is encoded by the apeE gene (P. Collin-Osdoby and C. G. Miller, Mol. Gen. Genet. 243:674-680, 1994). This paper reports the cloning and nucleotide sequencing of the S. typhimurium apeE gene as well as some properties of the esterase that it encodes. The predicted product of apeE is a 69.9-kDa protein which is processed to a 67-kDa species by removal of a signal peptide. The predicted amino acid sequence of ApeE indicates that it is a member of the GDSL family of serine esterases/lipases. It is most similar to a lipase excreted by the entomopathogenic bacterium Photorhabdus luminescens. The Salmonella esterase catalyzes the hydrolysis of a variety of fatty acid naphthyl esters and of C6 to C16 fatty acid p-nitrophenyl esters but will not hydrolyze peptide bonds. A rapid diagnostic test reported to be useful in distinguishing Salmonella spp. from related organisms makes use of the ability of Salmonella to hydrolyze the chromogenic ester substrate methyl umbelliferyl caprylate. We report that the apeE gene product is the enzyme in Salmonella uniquely responsible for the hydrolysis of this substrate. Southern blot analysis indicates that Escherichia coli K-12 does not contain a close analog of apeE, and it appears that the apeE gene is contained in a region of DNA present in Salmonella but not in E. coli.

In vivo transcripts of the S-layer-encoding structural gene of the archaeon Methanococcus voltae.

The 5' region of the S-layer-encoding structural gene (sla) of Methanococcus voltae was sequenced. The sequence information was then used to identify the in vivo transcription products of the gene. We observed three transcripts, and upstream from each transcription start point was a region with similarity to the Box A consensus sequence observed in archaeal promoters. In two of the three cases, two Box A sequences were present in tandem. This arrangement may play a role in the high level of gene expression expected for the sla gene. Presumptive archaeal Box B signatures were also identified.

The DNA polymerase gene from the methanogenic archaeon Methanococcus voltae.

Previous studies have identified intervening sequences that encode homing endonucleases within the genes encoding several archaeal DNA polymerases. We report the sequence of the gene encoding the DNA polymerase of Methanococcus voltae and describe evidence that it lacks analogous intervening sequences.