Related Experiment Videos
Abundant mRNAs in the squid light organ encode proteins with a high similarity to mammalian peroxidases
S I Tomarev1, R D Zinovieva, V M Weis
1Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892.
Abstract:
A library derived from mRNA in the bacterial light organ of the squid, Euprymna scolopes, contained an unexpectedly high proportion of cDNAs that encode proteins with approximately 30% similarity to a family of mammalian peroxidases (PO) including myelo-PO, eosinophil PO, and thyroid PO (donor:hydrogen-peroxide oxidoreductase; EC 1.11.1.7). Two nearly full-length cDNAs were determined to encode putative PO of nearly 93 kDa each that are 97% identical in amino acid sequence to each other. Each contains four potential glycosylation sites, and His416, believed to be within the active site of the human PO, is conserved in the putative PO from the squid light organ. The mRNAs for the putative squid PO were approximately 250 times more abundant in the tissue housing the bacterial symbiont than in the ocular lens or mantle and were undetectable in the light organ lens. By analogy with the bacteriocidal function of PO in mammalian neutrophils, the putative squid PO may be important for modulating or limiting the population of bacteria within the light organ. The possibility that the squid light organ contains a high concentration of PO raises the possibility that the light organ lens is under oxidative stress, providing a possible rationale for the recruitment of its aldehyde dehydrogenase-like crystallin.
Insights
Researchers discovered novel peroxidases (PO) in the squid light organ, potentially regulating bacterial populations. These findings suggest a role for PO in symbiotic relationships and oxidative stress management.
Area of Science:
- Molecular Biology
- Biochemistry
- Marine Biology
Background:
- The bacterial light organ of the squid Euprymna scolopes houses symbiotic bacteria.
- Mammalian peroxidases (PO) play roles in immune defense and oxidative processes.
Purpose of the Study:
- To investigate the molecular components of the squid Euprymna scolopes light organ.
- To identify and characterize novel proteins, particularly those with potential enzymatic activity.
Main Methods:
- Construction and screening of a cDNA library derived from E. scolopes light organ mRNA.
- Sequence analysis of identified cDNAs to determine protein identity and characteristics.
- Quantitative analysis of mRNA expression levels in different squid tissues.
Main Results:
- A high proportion of cDNAs encoded proteins with significant similarity to mammalian peroxidases (PO).
- Two nearly full-length cDNAs identified putative POs (approx. 93 kDa) with 97% sequence identity.
- Squid PO mRNA was highly abundant in the light organ housing bacteria, but absent in the light organ lens.
Conclusions:
- The putative squid POs may function in modulating bacterial populations within the light organ, analogous to mammalian neutrophil POs.
- High PO concentration suggests potential oxidative stress in the light organ, possibly explaining the presence of aldehyde dehydrogenase-like crystallin.