Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE building ( building_id text, name text, street_address text, years_as_tallest text, height_feet number, floors number )
TABLE: CREATE TABLE protein ( common_name text, protein_name text, divergence_from_human_lineage number, accession_number text, sequence_length number, sequence_identity_to_human_protein text, institution_id text )
TABLE: CREATE TABLE institution ( institution_id text, institution text, location text, founded number, type text, enrollment number, team text, primary_conference text, building_id text )

### Question ###
How many proteins are associated with an institution in a building with at least 20 floors?

### Accurate SQL ###

SELECT COUNT(*) FROM institution AS T1 JOIN protein AS T2 ON T1.institution_id = T2.institution_id JOIN building AS T3 ON T3.building_id = T1.building_id WHERE T3.floors >= 20