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Sea urchin protease specific to the SPKK motif in histone
Abstract:
A protease activity specific to spermatogenous histones was found in the egg extract of sea urchin. The enzyme responsible for this activity, named SPKK protease because of its substrate specificity, was purified as a monomeric 28 kDa protein. SPKK protease activity is inhibited by leupeptin and is specific to the repeat of sequences like Ser-Pro-Lys-Lys (the SPKK motif) [Suzuki, M. (1989), EMBO J. 8, 797-804]. The DNA-binding sites of sea urchin spermatogenous histones H1 and H2B, which protect the linker DNA of chromatin, are made up of sequences rich in the SPKK motif. SPKK protease may contribute not only to the unpacking of sperm chromatin but also to transcription activation of the male origin gene at fertilisation. SPKK protease resembles another protease activity on nucleolin [Burger et al. (1982) Eur. J. Biochem. 128 475-480] in its characteristics.
Insights
A novel protease, SPKK protease, was identified in sea urchin eggs, specifically targeting spermatogenous histones. This enzyme may play a role in sperm chromatin decondensation and gene activation during fertilization.
Area of Science:
- Molecular Biology
- Developmental Biology
- Biochemistry
Background:
- Sea urchin egg extracts contain protease activity specific to spermatogenous histones.
- Histones H1 and H2B in sea urchin sperm contain DNA-binding sites rich in the Ser-Pro-Lys-Lys (SPKK) motif.
Purpose of the Study:
- To identify and characterize the enzyme responsible for protease activity against spermatogenous histones in sea urchin egg extracts.
- To investigate the potential role of this protease in fertilization processes.
Main Methods:
- Purification of the SPKK protease from sea urchin egg extract.
- Characterization of the purified enzyme's molecular weight (28 kDa) and substrate specificity.
- Assay of protease activity and inhibition studies using leupeptin.
Main Results:
- A 28 kDa monomeric protein, SPKK protease, was purified.
- The enzyme exhibits specificity for sequences containing the SPKK motif.
- SPKK protease activity is inhibited by leupeptin.
Conclusions:
- SPKK protease is a key enzyme involved in modifying sperm chromatin.
- This protease may facilitate sperm chromatin decondensation and activate male genes during fertilization.
- SPKK protease shares characteristics with protease activity observed on nucleolin.