Structural Basis for the Acyltransferase Activity of Lecithin:Retinol Acyltransferase-like Proteins

• Published in: The Journal of biological chemistry 2012-07, Vol.287 (28), p.23790-23807
• Main Authors: Golczak, Marcin, Kiser, Philip D., Sears, Avery E., Lodowski, David T., Blaner, William S., Palczewski, Krzysztof
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; Acylation; Acyltransferases - chemistry; Acyltransferases - genetics; Acyltransferases - metabolism; Amino Acid Sequence; ARCHITECTURE; BASIC BIOLOGICAL SCIENCES; Biocatalysis; BIOLOGY; CATALYSIS; Catalytic Domain; Chromatography, High Pressure Liquid; CRYSTAL STRUCTURE; Crystallography, X-Ray; Cysteine - chemistry; Cysteine - genetics; Cysteine - metabolism; Electrophoresis, Polyacrylamide Gel; Enzyme Catalysis; Enzyme Stability; ENZYMES; Enzymology; EXPENDITURES; Humans; LECITHINS; Lipase; LIPASES; LIPIDS; Mass Spectrometry; METABOLIC DISEASES; Models, Molecular; Molecular Sequence Data; NEOPLASMS; Phosphatidylcholine; Phospholipases A2; Phospholipases A2, Calcium-Independent - chemistry; Phospholipases A2, Calcium-Independent - genetics; Phospholipases A2, Calcium-Independent - metabolism; Phospholipids - metabolism; Protein Binding; Protein Structure, Tertiary; PROTEINS; RESOLUTION; Sequence Homology, Amino Acid; Structural Biology; Substrate Specificity; TARGETS; THIOLS; TOPOLOGY; TRIGLYCERIDES; Tumor Suppressor Proteins - chemistry; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism; VERTEBRATES
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.361550

Lecithin:retinol acyltransferase-like proteins, also referred to as HRAS-like tumor suppressors, comprise a vertebrate subfamily of papain-like or NlpC/P60 thiol proteases that function as phospholipid-metabolizing enzymes. HRAS-like tumor suppressor 3, a representative member of this group, plays a key role in regulating triglyceride accumulation and energy expenditure in adipocytes and therefore constitutes a novel pharmacological target for treatment of metabolic disorders causing obesity. Here, we delineate a catalytic mechanism common to lecithin:retinol acyltransferase-like proteins and provide evidence for their alternative robust lipid-dependent acyltransferase enzymatic activity. We also determined high resolution crystal structures of HRAS-like tumor suppressor 2 and 3 to gain insight into their active site architecture. Based on this structural analysis, two conformational states of the catalytic Cys-113 were identified that differ in reactivity and thus could define the catalytic properties of these two proteins. Finally, these structures provide a model for the topology of these enzymes and allow identification of the protein-lipid bilayer interface. This study contributes to the enzymatic and structural understanding of HRAS-like tumor suppressor enzymes. Background: The enzymology of aminophospholipid-processing enzymes is not well understood. Results: Structures of HRAS-like tumor suppressors resemble those of thiol proteases with Cys-His-His catalytic triad. Conclusion: An aminophospholipid acyl group first modifies the Cys residue of HRAS-like tumor suppressor enzymes before it is transferred onto a second substrate. Significance: This study provides a structural basis for the enzymatic mechanism of HRAS-like tumor suppressors.