[Research in similarities between EEP34 and lipocortin].

Area of Science:

• Ophthalmology
• Biochemistry
• Cell Biology

Background:

• The lens fiber membrane contains EDTA-extractable protein (EEP), a significant extrinsic protein.
• Understanding EEP's function is crucial for comprehending lens structure and physiology.

Purpose of the Study:

• To characterize the molecular properties of calf lens EEP.
• To investigate the interactions of EEP with other cellular components.
• To explore the potential identity and function of EEP within the lens.

Main Methods:

• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to separate EEP bands.
• Analysis of EEP's interaction with F-actin and liposomes using calcium (Ca2+) dependence.
• Two-dimensional gel electrophoresis to compare calf EEP with lipocortin.
• Immunological cross-reactivity testing using antibodies against lipocortin.

Main Results:

• Calf lens EEP separated into three major bands on SDS-PAGE with molecular weights of 34, 33, and 32 kilodaltons (kd).
• EEP's combination with F-actin and phospholipid-containing liposomes was calcium-dependent.
• Partial overlap was observed between calf EEP spots and lipocortin spots in two-dimensional gel electrophoresis.
• The 34 kd EEP protein demonstrated cross-reactivity with an antibody against pig aorta lipocortin.

Conclusions:

• Calf lens EEP comprises proteins of approximately 32-34 kDa.
• EEP exhibits calcium-dependent interactions with F-actin and phospholipids.
• Evidence suggests calf EEP is related to lipocortin, a known phospholipase A2 inhibitor.
• These findings indicate a potentially important functional role for EEP in the lens.